Is a young man sinful for the suicide of a person with whom he quarrelled and insulted, and who then committed suicide two days later? Is it permissible to ask for mercy for him, while seeking forgiveness for being the cause of his suicide?

People should be treated with kindness, benevolence, and goodness, as Allah Almighty says: (And speak to people good words), and the Prophet, peace and blessings be upon him, said: "Deal with people with good manners." Quarrelling and despising a Muslim is a mistake that necessitates repentance, as the Prophet, peace and blessings be upon him, said: "It is enough evil for a person to despise his Muslim brother." A man's suicide is forbidden, but you bear no sin for his act, and seeking forgiveness for him is permissible.