God: "I looked for someone to take a stand for me, and stand in the gap" (Ezekiel 22:30)
Sexual lust is definitely a sin and the catalyst for masturbating. But is the actual act itself, apart from lusting in the mind a sin? I believe the answer to that is yes. Masturbation is an aberrant form of sexual intercourse which is to be enjoyed by a married couple only. There is nothing in the Bible which gives approbation to celibate sex [by oneself].