Is it obligatory to advise someone who knows the Islamic ruling on a prohibited matter and intends to commit it, even if there is a possibility that they may not respond to the advice?

Advice is a duty upon a Muslim towards his brother. It should be given with gentleness, kindness, and wisdom, especially with parents. Advice does not cease to be obligatory merely by the assumption that it will not be beneficial; rather, it must be offered unless it is known with certainty that the advised person will not accept it, in which case its obligation is lifted. One should continue to advise and vary the methods, while keeping in mind the intention of drawing closer to Allah and supplicating for the advised person’s guidance.