Is he who abstains from advising his friends who commit sins and iniquities, sinful, knowing that they are aware of the unlawfulness of their actions and averse to advice?

Whoever sees an evil must change it according to their ability. If one of your companions commits an evil, you must denounce it to him and clarify its prohibition by Islamic law. If he does not desist from committing it after being denounced, then you must abandon him and his company, for Allah Almighty says: "And He has already sent down to you in the Book that when you hear the verses of Allah being denied and ridiculed, then do not sit with them until they engage in another conversation. Indeed, you would then be like them." Abandoning denouncement when one is able to do so makes one a partner in sin. Therefore, it is advisable to choose righteous companions, for the Prophet, peace and blessings be upon him, said: "Do not accompany anyone but a believer, and let no one eat your food except a pious person."