Lu 22:36 Then said he (Jesus) unto them, But now, he that hath a purse, let him take it, and likewise his scrip: and he that hath no sword, let him sell his garment, and buy one.
An excellent article on the Biblical basis for self-defense:
Is the Best Defense a Good Book?
http://davekopel.com/Religion/Is-the-best-defense-a-good-book.pdf