(36) باب بَيَانِ كَوْنِ الإِيمَانِ بِاللَّهِ تَعَالَى أَفْضَلَ الأَعْمَالِ
It is narrated on the authority of 'Abdullah b. Mas'ud that he observed. I asked the Messenger of Allah (ﷺ) which deed was the best. He (the Holy Prophet) replied:
Prayer at its appointed hour. I (again) said: Then what? He (the Holy Prophet) replied: Kindness to the parents. I (again) said: Then what? He replied: Earnest endeavour (Jihad) in the cause of Allah. And I would have not ceased asking more questions but out of regard (for his feelings).
Reference: Sahih Muslim 85 a
In-book reference: Book 1, Hadith 158
USC-MSA web (English) reference(deprecated numbering scheme): Book 1, Hadith 151