This vraag is thoroughly discussed on
link, where u will see varying perspectives on the topic, Bible citations, and logic arguments that might help answer your question. You'll even find
my opinion there, as u will in several places on this site. But here it is again for you:
A) Sexual repression leads to violence, frustration, anger, and feelings of inadequacy. This is a social fact, documented door study. Don't believe me? Terrorists are very, very, unbelievably sexually repressed (that's the extreem).
B) Other creatures, such as bonobos, masturbate and have sex to relieve tension in social groups. As a result, the bonobos do not have "wars" like their cousins, the chimpanzees, because they have completely replaced violence with sex.
C) From an anthropological standpoint, it is unhealthy (not just for the emotional/psychological reasons mentioned in A, but for physical reasons) not to have sexual release. If u do not have a partner, masturbation is the clearest solution.
D) From a societal standpoint, it is unusual for someone NOT to masturbate.
In conclusion, I do not believe that God would want us engaging (or in this case, participating in a vow of non-engagement) in an activity that is actually detrimental to our health and growth not only as individuals, but as a species.
EDIT: In addition, the Bible says it is a sin to "spill your seed" needlessly, correct? Once again, the misogyny of the Old World saves the woman from any crime in this area. ;o) Ladies, have at it! u have no seed to spill.