Abstaining from meat is a form of fasting. Fridays have been a day of fasting for Christians from the beginning. The Didache, a Church manual written in the first century says:But let not your fasts be with the hypocrites, for they fast on the second and fifth day of the week. Rather, fast on the fourth day [Wednesday] and the Preparation [Friday]. (Didache, chap. 8)
Jesus seems to have predicted Friday fasts when he said:
20The days will come, when the bridegroom is taken away from them, and then they will fast in that day. (Mark 2:20)
When was Jesus taken from his disciples? What day of the week did Jesus die? Friday.
Jesus gave the leaders of his Church the authority to make binding decisions in Matthew 16:19 and 18:17.
19 I will give you the keys of the kingdom of heaven, and whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven." (Matthew 16:19)
An example of the exercise this binding authority can be found in Acts 15.
4 As they went on their way through the cities, they delivered to them for observance the decisions which had been reached by the apostles and elders who were at Jerusalem. (Acts 16:4)