Is it permissible for a young man in his twenties to remind the worshippers of matters concerning their religion after every congregational prayer in the mosque?

Whoever undertakes the task of teaching people and reminding them of their religious matters must have insight into what they teach. If the questioner is qualified, let him remind his brothers in the mosque and elsewhere; for there is great reward in teaching people and inviting them to goodness. Allah Almighty said: (And let there be [arising] from among you a nation inviting to [all that is] good, enjoining what is right and forbidding what is wrong, and those will be the successful) (Quran 3:104). And He, glorified be He, said: (Say, "This is my way; I invite to Allah with insight, I and those who follow me.") (Quran 12:108). And the Prophet, peace and blessings be upon him, said: (Convey from me, even if it is a single verse), and (Let the present convey to the absent), and (Indeed, Allah and His angels and the inhabitants of the heavens and the earths, even the ant in its hole and even the fish, pray for the one who teaches people good).

Emphasis must be placed on sincerity to Allah Almighty in this work, choosing beneficial topics, ensuring the authenticity of hadiths and sayings, and considering the circumstances of those being taught to avoid boring them.