The acceptability of one’s deeds and act of worship depends of Ikhlās [sincerity] and on Taqwā [Fear of Allāh]. This is stated in a dialogue between Hābīl and Qābīl. The deeds of a person who has no Taqwā in him is not accepted.
For this reason, the learned among the righteous elders (Salaf) have said that this verse is a shot in the arm for those who are devoted to acts of worship and do deeds in the hope of finding the pleasure of Allāh. And this is the reason why Sayyidnā Āmir ibn ‘Abdullāh – may Allāh be pleased with him – was crying at the time of his death. People around him asked, ‘As for you, you have been busy doing your ‘Ibād’āt (acts of worship) and good deeds throughout your life, why then do you weep?’ He replied, ‘You are saying this and ringing in my ears is the saying of Allah ‘إنما يتقبل الله من المتقين’ (Allāh accepts only from the God-fearing [5:27]). I just don’t know if any of my ‘Ibādah will be accepted, or not.
Hadhrat Abdullah Ibn Mas’ūd رضي الله عنه said, ‘If I become certain that Allāh تعالى has accepted some deed of mine, then I would not surrender this blessing even if the whole world were to turn into solid gold and pass into my possession, in fact, I would take it to be nothing as compared to that blessing.’
Sayyidnā Abū Dardā رضي الله عنه said, If it stands that one Salāh of mine has found acceptance with Allāh then that is far more than a whole world full of blessings for me.’
Sayyidnā ‘Umar Ibn ‘Abd al-‘Azīz رضي الله عنه gave the following advice to a person in a letter he wrote to him: I tell you to hold onto Taqwā, without it which no deed is accepted and mercy is not shown to anyone except those who observe Taqwā; and without it there is no Divine reward on anything. There are many who preach it but there are very few who practice it.’
And Hadhrat Alī رضي الله عنه said, “Even the smallest deed done with Taqwā is not small. How can a deed which has been accepted be called ‘small’?”[Ma’āriful Qur’ān, Volume 3, page 128-129]