Does the reward for righteous deeds cease if a Muslim stops performing them due to laziness?

This statement is incorrect and has no proof. The evidence shows that every righteous deed, done sincerely for the sake of Allah and in accordance with the Sharia (definition), is accepted and its reward is not annulled merely by discontinuing it. As Allah Almighty said: "Indeed, We will not allow to be lost the reward of any who did well in deeds." And the Prophet (peace be upon him) said: "Indeed, Allah does not wrong a believer concerning a good deed; he is given for it in this world and rewarded for it in the Hereafter." This does not contradict the Sharia's urging to persevere in righteous deeds, as perseverance in them is better.