Allah, the Wise, has said:
اَنَّ الَّّذِينَ يُؤذُونَ اللهَ وَ رَسُولَهُ لَعَنَهُمُ اللهُ فِي الدُّنْياَ وَ الْآخِرَة
"Verily those who annoy Allah and His Messenger - Allah has cursed them in this World and in the Hereafter." 
The Holy Prophet (s.a.w.) said:
لاَ يَحِلُّ لِلْمُسلِمِ اَن يُشِيْرَ اِلَى اَخِيهِ بِنَظْرَةٍ تُؤذِيهِ
"It is not permissible for a Muslim to look at a brother Muslim in a manner that hurts and inconveniences him." 
All creatures belong to the household of (the Creation of) God and pre-eminent amongst them are the believers. Any person who is of benefit to the creation, becomes the beloved of God, while one who harasses and inconveniences others, especially the believers, in any way, is as if he has declared war upon God.
On the Day of Judgment, God shall call out: Where are those who harassed and tormented My friends in the world. A group of people whose bodies would be bare of flesh, would step forward whereupon God shall order them to be hurled into Hell.
Thus, it is essential to refrain from hurting and harassing others - parents, neighbours, friends, and so on. If one has committed this act, forgiveness ought to be sought from those concerned.
1 – Harassment of Imam Sajjad (a.s.)
During the time of Imam Sajjad, there lived a person in Madinah, who used to make people laugh to earn his livelihood.
Some people suggested that they should invite Imam Sajjad (a.s.) and allow this person to make him laugh a little in an attempt to sidetrack the Imam from his deep lamentation. They gathered together and were on their way to his house when they saw him coming towards them, accompanied by two of his slaves. When the Imam (a.s.) came near, the comediantook the cloak off Imam Sajjad’s (a.s.) shoulders and put it over his own. The people around burst out laughing when they saw this antic.
The Imam (a.s.) inquired, "Who is this person?"
The people around him answered, "He is a person who makes people laugh and receives money from them for his antics."
"Inform him that those who expend their lives in a futile way performing absurd acts shall be the losers on the Day of Judgment," advised the Imam (a.s.).
After hearing this, the comedian stopped his annoying behaviour and mended his ways.
2 – Qaroon and Musa (a.s.)
Prophet Musa (a.s.), in the course of propagating his religion, had to face severe adversity and hardship from the likes of Firo'un, Bala’m, Bao’ora and even his cousin Qaroon. Qaroon was immensely rich and possessed so much wealth that several strong youths were required to carry just the keys of his treasury. He was one of the high ranking and influential nobles, who used to oppress his inferiors.
Musa (a.s.), in compliance with God’s orders, sought zakaat from him, but Qaroon used to say:
"I too possess knowledge of the Torah and am not inferior to Musa in any way; why should Ipay zakaat to him?"
Eventually, his arrogance forced him to resort to dirty tactics to try to demean Prophet Musa. He approached a woman who was of bad character but was also extremely beautiful and attractive.
He said to her, "I shall pay you a hundred thousand dirhams provided that tomorrow, when Musa (a.s.) is delivering a sermon to Bani Israel, you shout out in front of the people that Musa has committed adultery with you."
The woman accepted the offer. The next day Bani Israel had gathered and Musa (a.s.), with the Torah in hand, was engaged in preaching to them. Qaroon, in all his finery, was also present in the crowd along with his attendants. Suddenly, the woman stood up, but as she looked at the saintly face of Musa (a.s.), she experienced a change of heart and cried out aloud:
"O’ Musa! Do know that Qaroon has promised me a hundred thousand dirhams if I accuse you, in front of Bani Israel, of having committing adultery with me; but (I declare that) you have never committed such an act and God has protected your holy personality from such uncleanness."
When he heard this, Musa (a.s.) was devastated and heartbroken, and he cursed Qaroon by saying, "O’ Earth! Seize Qaroon and take him within you."
Upon Divine orders, the ground underneath split apart and Qaroon and all his wealth fell in.
According to another report, Musa had been preaching the people about his Sharia’h when, in the course of his lecture, he said:
"A person who does not have a spouse and indulges in adultery shall be punished with one hundred lashes and a person who possesses a spouse and (yet) commits adultery, shall be stoned to death."
At that moment, Qaroon stood up and remarked, "(Would this be true) even if you were to commit such an offense?"
"Yes," replied Musa.
"The Bani Israel are under the impression that you have committed adultery withsuch and such woman."
"Bring the lady here," demanded Musa. "If she testifies to this claim, you are at liberty to act according to the law."
The woman was brought before Musa (a.s.) who, placing her under oath to speak the truth, asked her:
"Have I committed adultery with you?"
The woman suddenly began to experience a change in her thinking and gave an answer which was opposite to what she had intended.
"No! They lie", she said. "Qaroon paid me such and such amount in order that I level this accusation at you."
Qaroon stood humiliated while Musa (a.s.) began weeping, fell down in prostration and supplicated:
"O’ God! Your enemy has hurt me and sought to disgrace me by means of calumny. If I am Your Prophet, grant me ascendancy over him."
Then he cursed Qaroon whereupon Divine punishment overtook him and the earth consumed him.
3 – It is Forbidden to Hurt a Mu'min
Husain Ibn Abi al-A’laa narrates:
I started out for Makkah in the company of twenty other persons. At every resting place, I would slaughter a goat, in order to provide the people with food. When I arrived in the presence of Imam Sadiq (a.s.), he said to me:
"O’ Husain! Woe be unto you that you hurt and cause inconvenience to the Mu'mineen."
"I seek refuge in God from such an act," I said.
He explained, "I have been informed that at every resting-place you used to slaughter a goat for your companions."
"Yes, but By God, it was only for His happiness that I acted in this manner".
The Imam (a.s.) continued, "Don’t you realize that amongst the group there were some, who desired to possess wealth so they too could perform good deeds like you, but not having the means, they have become upset."
"I repent over my actions and resolve never to act in that way again," I said.
The Imam (a.s.) advised, "A Mu'min, in the eyes of God, is more honourable than the angels, the mountains, the seven skies, the seven earths and everything that exists in them."
4 – Harassing Amirul Mu'mineen (a.s.) is akin to Harassing the Holy Prophet (s.a.w.)
A'mr Ibn Shaas Aslami, one of the companions present during the treaty of Hudaibiyah, narrates:
Once, A'li (a.s.) and I had embarked upon a journey towards Yemen. During the journey, I happened to get upset with him and my heart was filled with malice towards him.
As I returned from the trip, I proceeded to the mosque and complained to the people about his behaviour. Unfortunately, it so happened that my words eventually reached the ears of the Holy Prophet (s.a.w.).
One morning, on entering the mosque, I noticed the Holy Prophet (s.a.w.) present there together with a few of his companions. As soon as his eyes fell upon me, he gazed at me in anger and continued to do so till I had seated myself.
"O’ A'mr! By God, you have surely harassed me!" he said crossly.
I exclaimed, "I seek refuge in God from ever harassing or annoying you".
He said, "Yes, you have troubled me for whoever has troubled A'li (a.s.) has troubled me too."
5 – Maltreatment by Mutawakkil
One of the worst Abbasid caliphs was Mutawakkil, who left no stone unturned in his attempt to harass and torment Imam Hadi (a.s.), the descendants of the Holy Prophet (s.a.w.), the Shiites and the pilgrims of Imam Husain (a.s.).
The governor of Madinah, A'bdullah Ibn Muhammad, acting on Mutawakkil’s instructions, troubled Imam Hadi (a.s.) to such an extent that the Imam (a.s.) was compelled to write a letter of complaint to Mutawakkil.
Later on, Mutawakkil forced the Imam (a.s.) to move from Madinah to Saamarra. Here, he initiated a fresh wave of persecution and harassment, some instances of which follow:
One night, Mutawakkil called Sa’eed, his doorkeeper, and instructed him to climb into Imam’s house and snoop around with a view to finding wealth or weapons. If they were found, he should confiscate them.
On another occasion, relying on a false accusation, he ordered a group of Turks to rush into the Imam’s house, take possession of everything they could find and bring him to the court. When the Imam (a.s.) was brought to the court, Mutawakkil was busy consuming wine and (out of mockery) offered it to the holy Imam (a.s.) and said: "Recite poetry for me!"
On yet another occasion, he had the Imam (a.s.) brought before him and ordered four Khazar Jilfi slaves to attack him with swords, but the Imam (a.s.), utilizing the power of Imamate, miraculously repulsed this attack.
In the year 237 A.H., Mutawakkil ordered the grave of Imam Husain (a.s.) and the houses in its vicinity to be destroyed and wanted the area to be used for farming and cultivation.
He decreed that a hand or a leg of anyone who came for the pilgrimage of Imam Husain (a.s.) should be amputated.
U'mar Ibn Faraj, who was made the governor of Makkah and Madinah by Mutawakkil, was ordered to prevent the people from helping or showing kindness to the descendants of the Holy Prophet (s.a.w.). The people, out of fear, refrained from assisting these descendants whose condition became so miserable and adverse that they did not even have proper garments to wear. This harassment and torture reached such a stage that Muntasir, Mutawakkil’s son, out of love for Amirul Mu'mineen (a.s.) was eventually promptedto murder his own father.
 Holy Qur'an, ch. Al-Ahzaab (33), vs. 57.
 Jaame’ al-Sa’adaat, vol. 2, pg. 215.
 Darsi Az Akhlaaq, pg. 120; Al-Amaali (Sheikh Mufid), pg. 128.
 Hikaayat-ha-e-Shanidani, vol. 5, pg. 122; Bihaar al-Anwaar, vol. 13, pg. 253.
 Namunah-e-Ma'arif, vol. 2, pg. 453; La-aali al-Akhbaar, pg. 135.
 Daastaan-hai Az Zindagi-e-A'li, pg. 112; Mustadrak al-Sahihain, vol. 3, pg. 122.
 These were stupid, brutish and wee-eyed people.
 Muntahal Aa’maal, vol. 2, pgs. 378 – 384