Imam Ali (A.S) was one of the best worshippers of his time. His worship was excellent both in quantity –the amount of worship– and in quality –sincerity, full attendance, presence of heart, and observation of Allah.
Amiral Mu’minin (A.S) stated, “Some people worship the Almighty Allah in hope of reward; this is the worship of merchants. Some worship Allah for fear of punishment; this is the worship of servants. Still some others worship the Exalted Allah for thanking Him; and this is the worship of the tolerant.” [Biharul Anwar, Vol 41, p. 14]
He has also stated, “O Allah! I do not worship you for fear of punishment or in hope of reward; rather, I know you worthy of worshipping so I worship you.” [Biharul Anwar, Vol 41, p. 14]
Someone told Imam Ali (A.S), “Have you seen your Lord that you worship Him?” Imam Ali (A.S) answered, “Woe be on you! I do not worship the Lord Who I have not seen.” The questioner asked, “How have you seen Him?” Imam Ali (A.S) replied, “Human eye cannot see Allah, rather his heart can perceive Allah by real belief.” [Biharul Anwar, Vol 41, p. 16]
Qushayri writes, “When the prayer time came Amiral Mu’minin’s (A.S) face discolored and his body shook. He was asked about the reason for this change of state. Imam Ali (A.S) answered, ‘It is the time for returning a trust, which the Almighty Allah presented to the Heavens and the Earth and the mountains, but they could not bear accepting it. The weak human, however, accepted that trust. I wonder if I could have returned the trust well.’” [Biharul Anwar, Vol 41, p. 17]
Imam Sajjad (A.S) read the book in which Ali’s worship was recorded. Then he put the book down and said, “Who can worship like Ali Ibn Abi Talib (A.S)?” [Biharul Anwar, Vol 41, p. 17]
Ibn Abbas says, “Two camels were granted to Prophet Muhammad (P.B.U.H). He told his companions, ‘I will give one of these camels to the one who performs a two- rak’ah (unit) prayer, with complete attention to Allah and without thinking of worldly affairs.’ Only Ali Ibn Abi Talib (A.S) answered this request. Then Prophet Muhammad (P.B.U.H) granted both camels to him.” [Biharul Anwar, Vol 41, p. 18]
Habbah Arani says, “One night Nuwf and I were sleeping in Darul ‘Imarah yard. We saw Imam Ali (A.S) who had put his hand on the wall while walking and said like a heartsick person, ‘Behold! In the creation of the heavens and the earth, and the alternation of night and day, there are indeed Signs for men of understanding…’ [Surah ‘Ali ‘Imran 3, 190-200]
He repeated these Quranic verses, walking infatuatedly. Imam Ali (A.S) told me, ‘O Habbah! Are you awake?’ I answered, ‘Yes I am. You behave like this (out of Allah’s fear). What should we do?’ Imam Ali (A.S) began weeping and said, ‘O Habbah! The Almighty Allah is closer to you and I than our neck vessel; nothing hides us from Him.’”
Then Imam Ali (A.S) told Nuwf, ‘Are you awake?’ Nuwf replied, ‘O Amiral Mu’minin! I am awake. You made us cry tonight.’ Imam (A.S) stated, ‘If you cry in darkness of night for fear of Allah, your eyes will be illuminated on the Last Day.
O Nuwf! Everyone who drips a tear from Allah’s fear his sins will be forgiven. O Nuwf! Everyone who weeps from Allah’s fear and his loving and disliking is for Allah’s sake will have a high position. O Nuwf! Everyone whose affection is for Allah’s sake will prefer nothing to that affection. Everyone whose hatred is for Allah’s sake will not spend his hatred for his own sake. This way the real belief will be maintained and improved.’”
Then Imam Ali (A.S) preached us and said at last, ‘Fear Allah!” Then he said while leaving, “O Lord! I am wondering if you have ignored me or attended to me. I wish I knew how my stance is with these long sleeps and little thanking!’”
Habbah has said, “By Allah that he was in the same state until the dawn.” [Biharul Anwar, Vol 41, p. 22]
Mu’awiyah once told Dharar Ibn Dhamarah, “Describe Ali for me.” He said, “I saw Ali (A.S) in some occasions worshipping in darkness of night. He had grasped his beard, agonizing like a snake-bitten person, weeping, and saying, ‘O world! Go way from me! Do you come to me? It is not your time. Deceive others, not me! I do not need you. I divorce you three times. Your period is short, your value is little, and my desire for you is scarce. Alas, my provisions are little, the travel is long, the destination is great, and the path is difficult!’” [Biharul Anwar, Vol 40, p. 345
source : sibtayn