What is the expiation for one who imagines his friend and commits sodomy with him while masturbating?

Thinking about your friend in the aforementioned manner is Islamically forbidden, and masturbation is also forbidden. We advise you to hasten to marry in order to protect your chastity. For whoever abstains from the forbidden, Allah will help him, and whoever marries for chastity, Allah will assist him. Allah Almighty says: "And let those who find not [the means for] marriage abstain until Allah enriches them from His bounty," and He says: "And marry the unmarried among you." In the Hadith: "Three are rightfully due Allah's help... and the one who marries, seeking chastity." Increase your fasting and supplication, fill your free time with what is beneficial, ponder upon Allah's blessings and the conditions of the people of the Hereafter, and read books on spirituality and the biographies of the Salaf. Your friend has no right over you, but do not mix with him or be alone with him, lest Satan tempt you.