Question: where in bible does it say not to eat meat on good friday?
Answer: From my point of view, it's a Romans 14:3 issue: The one who eats everything must not treat with contempt the one who does not, and the one who does not eat everything must not judge the one who does, for God has accepted them. So it's okay if you want to fast from meat on Fridays, but it's not necessary at all.