What is the ruling on breaking a vow to abstain from masturbation for two months, and on praying to God for the death of one's dearest friend upon committing it, and is expiation for the oath obligatory given that the supplication is now disliked?

Masturbation is forbidden, and one must abstain from it forever. A vow to abandon something already forbidden is not valid and entails nothing according to the majority of scholars, because it is a foregone conclusion. However, some scholars have held that it is binding, and an expiation for breaking an oath (kaffarat yamin) is due for whoever fails to fulfill it. Supplicating against a friend is injustice and sin, and it will not be answered, due to the Prophet’s (peace be upon him) saying: “The supplication of any servant continues to be answered as long as he does not supplicate for a sin or for the severing of kinship ties.”