> it says nothing of it in the bible
Ye have heard that it was said by them of old time, Thou shalt not commit adultery:
But I say unto you, That whosoever looketh on a woman to lust after her hath committed adultery with her already in his heart (Matthew 5, 27-28)
Marriage is honourable in all, and the bed undefiled: but whoremongers and adulterers God will judge. (Hebrews 13:4)
I say therefore to the unmarried and widows, it is good for them if they abide even as I. But if they cannot contain, let them marry: for it is better to marry than to burn.
It's a sin, to lust after a woman like that. To watch videos and to masturbate to it is adultery, and a sin. Paul tells the people that it is better to remain pure, and that if they cannot control themselves like he was able to (via no masturbation) then it is time to go out and find a good woman.