Allah, the Wise, says:
رَضِيَ اللهُ عَنْهُمْ وَ رَضُوا عَنهُ
"Allah is well-pleased with them and they are well-pleased with Him." 
Imam Sajjad (a.s) has said:
أََلصَّبْرُ وَ الرِّضاَ رَأْسُ طاَعِةِ اللهِ
"Patience and pleasure (over Divine acts) constitute the pinnacle of Allah's obedience." 
The attribute of Ridha is that a person remains pleased with occurrences - irrespective of whether they are to his liking or otherwise. This characteristic is a ray from the light of (Divine) cognizance such that a person possessing this attribute turns away from his own desires and seeks that which Allah has decreed for him instead. This is because attachment of the heart to worldly and material things is shirk, and therefore inconsistent with the attribute of Ridha.
It is amazing to observe those, who vociferously claim to be the servants and worshippers of Allah, complaining and grumbling over Divine decrees and acts. However, those who are truly cognizant, are in total submission and subservience to Allah - pleased and satisfied with Divine destinies, uncomplaining in the face of adversities, shortages and severity of trials, and contented and happy over things bestowed to them as well as those not granted to them.
1 – Complete Contentment with Allah
Jabir Ibn Abdullah Ansari, who had been of the companions of the Noble Prophet (s.a.w), had remained alive till the time of Imam Baqir (a.s) but had become old and blind by then.
Once, when he had arrived in the presence of the Imam (a.s), the Imam (a.s) inquired after his health, whereupon he said: "I find myself in a state such that I give preference to old age over youth, to sickness over soundness of health and to death over life!"
The Imam (a.s) responded by saying: "(On the contrary) if Allah makes me old, I prefer old age; if He desires to give me youth, I prefer youth; if He afflicts me with sickness, I desire sickness, and if He desires to favour me with sound health, I prefer soundness of health. If Allah wishes to give me death, I prefer death and if He wills to keep me alive, I desire to live."
As soon as Jabir heard the Imam's (a.s) speech he kissed his (a.s) face and said: "The Noble Prophet (s.a.w) had spoken the truth." He had said: "O' Jabir! You shall continue to live till you meet one of my children whose name shall be Baqir. He shall split open knowledge just as a cow splits open the earth."
2 – Pleased with Three Calamities
Hadhrat Isa [Jesus] (a.s) happened to come upon a blind, paralytic leper, whose disease had caused his very flesh to fall out of his body, and overheard him say: "Thanks to Allah, Who has cured me from the affliction that has seized numerous persons in its grasp!"
Isa (a.s) said to him: "O' Man! What is that affliction from which He has protected you?" The man replied: "O' Spirit of Allah! I am better off than one whose heart does not possess the cognizance of Allah - that cognizance which He has placed in mine."
Hearing this, Isa (a.s) said to him: "You have spoken correctly. Now give me your hand." Then taking hold of his hand, Isa (a.s) moved his holy hand over the leper's body, whereupon, the leper was immediately cured of his afflictions and was transformed into a man of charming appearance and good physique. Since he had remained pleased (and uncomplaining) over the tribulations that had afflicted him, Allah cured him of his ailments. Later on he went on to become one of the companions of Isa (a.s) and engaged in worship along with him (a.s).
3 – One of the Inmates of Paradise
Imam Sadiq (a.s) relates: "Once, Allah revealed to Hadhrat Dawud (a.s) to give glad tidings to Khalladah, the daughter of Aus, that she was of the inmates of Paradise and would be one of his (a.s) companions in it." Hadhrat Dawud (a.s) went to her house and knocked at her door, and it was Khalladah herself who opened it. She recognized him the moment she set her eyes upon him and so inquired: "Has something been revealed about me that you have come here?" When he (a.s) had replied in the affirmative, she said: "The revelation is probably for someone else, who resembles me in name!"
He (a.s) said: "No. The revelation has been for you. Tell me something about yourself."
She replied: "Whenever any pain, injury or misfortune would come to afflict me, I would exhibit patience and submit myself to Allah's pleasure. Neither would I desire any of the adversities to be warded away from me nor would I aspire for anything in exchange; I was always thankful to Him and His pleasure was the only thing that I coveted!"
When he heard this, Hadhrat Dawud (a.s) said: "It is because of this that you have reached such a rank that Allah has sent down this revelation about you."
Having related this incident, Imam Sadiq (a.s) said: "This is that very religion, which Allah has chosen for His righteous servants."
4 – Ammar in the Battle of Siffin
Ammar Yasir was one of the special companions of the Noble Prophet (s.a.w) possessed such a high degree of faith that the Noble Prophet (s.a.w) had stated: Ammar is replete with faith from head to toe, and faith has blended with (and become part of) his flesh and blood."
After the death of the Noble Prophet (s.a.w) he continued to be of those who fiercely supported Imam Ali (a.s), and when the battle of Siffin commenced, he fought on the side of the Imam (a.s). One day, coming out of the ranks of the Imam's (a.s) army, he stationed himself before the enemy forces and said: "O' Lord! You are aware that if I were to realize that Your happiness lies in my hurling myself into the seas, I would surely do so; and if I were to know that Your happiness lies in that I fling myself upon the point of a sword so that it enters into my stomach and emerges from the back of my neck, I would certainly do so. I know that today, Your happiness lies in waging a battle with these sinning and corrupt people, and had I known of an act that would have pleased You more, I would have surely opted for it."
Then, raising his voice, he said: "Whoever desires Allah's pleasure and does not desire to return to his wealth and children should come to me."
He was eventually martyred after displaying great valor and courage in the battlefield. Reaching his dead body, the Commander of the Faithful(a.s) sat down, placed his head upon his thighs and, as he wept, said: "O' Death! It appears that you are totally familiar with those, whom I love; you come and take them away from me."
5 – The Best Creation
Prophet Musa (a.s) requested to Allah: "O' Lord! Show to me who, from amongst all Your creations, is the best person who worships You." Allah revealed to him: "Proceed towards the village situated near the sea-shore and you shall find the person there."
Reaching there Musa (a.s) found a leper, who was engaged in praising and glorifying Allah. He (a.s) asked Jibra`il: "Where is the person whom I had sought from Allah?" Jibra`il pointed to the sick person and said: "This is the person! I am under instructions to take away his eyes; pay careful attention to what he shall say." Having said this, he pointed towards the leper's eyes and they suddenly popped out of their sockets. As soon as this happened, the leper said: "O' Allah! Till You desired you let me benefit from my eyes and now You have desired to take them away from me. O' The One! Who does good to me and provides me with goodness."
Approaching him, Musa (a.s) said: "O' Servant of Allah! I am a person whose prayers are always accepted; if you desire, I shall pray to Allah so that He returns your eyes to you."
The man said: "No, I do not desire it. Allah has desired this state for me and I am pleased with all that pleases Him."
Musa (a.s) said: "I heard you say: "O' The One! Who does good to me and provides me with goodness. What did you mean by these words?"
He said: "In this village I am the only one who is cognizant of Allah and worships Him (what goodness could be greater than this that He has made me aware and cognizant of Himself.)"
Musa (a.s) was overcome by astonishment and amazement, and as he turned back, he said to himself: "He is the greatest worshipper of Allah in the world."
 Suratul Mujadilah (58), Verse 22
 Jame~ al-Sa~adat, vol. 3, pg. 203
 Tadhkeratul Haqa`iq, pg. 85
 Pand-e-Tarikh, vol. 5, pg. 186
 Ilm-e-Akhlaq-e-Islami, vol. 3, pg. 262; Jami~ al-Sa~adat, vol. 3, pg. 208
 Dastan-ha Wa Pand-ha, vol. 3, pg. 37; Bihar al-Anwar, vol. 71, pg. 89
 Safinatul Bihar, vol. 2, pg. 275: ان عمارا ملئ ايمانا من قرنه الى قدمه و اختلط الايمان بلحمه و دمه
 Paighambar Wa Yaran, vol. 5, pp. 24-28; Bihar al-Anwar, vol. 8, pg. 524
 Namunah-e-Maarif, vol. 5, pg. 373; Shaytan, vol. 1, pg. 524