Is the return to religious commitment and performing acts of obedience with a sincere intention for the sake of Allah’s pleasure, or for the sake of worldly gain? And how do I know if the deed is pure or not?

All praise is due to Allah for returning to commitment and acts of obedience, and this is sufficient for success and salvation in this world and the Hereafter. One must strive with their intention to make it purely for Allah alone, and beware of the devil's whisperings. It is not a fault for a Muslim to ask Allah for the good of this world and the Hereafter, or to wish that Allah grants him more than He has granted his friends, as long as he does not envy them, nor wish for the cessation of blessings from them, nor perform good deeds solely with a worldly intention. A good deed, if initially mixed with a flawed intention, may become purely for Allah with striving and seeking sincerity. Knowing the sincerity of an action is something only Allah knows, and one of its signs is being granted success to perform obedience after obedience. Encouraging the brother to memorize the Quran is good, and Allah is capable of purifying his intention and making him beneficial to Islam and Muslims.