It is reported on the authority of ‘Abdullah that the Apostle of Allah observed: The best of’ the deeds or deed is the (observance of) prayer at its proper time and kindness to the parents.

It is reported on the authority of ‘Abdullah that the Apostle of Allah observed: The best of’ the deeds or deed is the (observance of) prayer at its proper time and kindness to the parents.
Source: HOTD