What are the two fundamental conditions for the acceptance of deeds by Allah, and what is meant by each of them?

For an action to be accepted, two conditions must be met: sincerity to Allah Almighty, and conformity to the Sunnah of the Messenger of Allah, peace and blessings be upon him. As Al-Fudayl ibn Iyad expressed it in his interpretation of "best in deeds": "the most sincere and the most correct." He clarified that an action is not accepted unless it is both sincere and correct. This is affirmed by the words of Allah Almighty: ﴿So whoever hopes for the meeting with his Lord, let him do righteous work and not associate anyone with the worship of his Lord.﴾