It is narrated on the authority of Abdullah bin Mas’ood (may Allah be pleased with him), who observed:
“I asked Allah’s Messenger (May peace be upon him) which deed was the best.” He (the Holy Prophet) replied: ‘The Prayer at its appointed hour.’ I (again) asked: “Then what?” He (the Holy Prophet) replied: ‘Kindness to the parents… (Sahih Muslim: 120)