Deuteronomy 16:1

1.Observe the month Abib. For what purpose God instituted the Passover, has already been shewn in the exposition of the First Commandment; for since it was a symbol of redemption, and in that ceremony the people exercised themselves in the pure worship of the One God, so as to acknowledge Him to be their only Father, and to distinguish Him from all idols, I thought that the actual slaying of the lamb should be introduced amongst the Supplements to the First Commandment. It only remains for us to speak here of what relates to the Sabbath. This then was the first solemn day, on which God would have His people rest and go up to Jerusalem, forsaking all their business. But mention is here made not only of the Paschal Lamb, but He also commands sheep and oxen to be slain in the place which He should choose. In these words He signifies that on that day a holy convocation was to be held; which is soon after more clearly expressed, for I have already given the two intermediate verses in the institution of the Passover itself, He therefore prohibits their slaying the Passover apart in their own cities, but would have them all meet in the same sanctuary. It has been elsewhere said that one altar was prescribed for them, as if God would gather them under one banner for the preservation of concord and the unity of the faith. What is added respecting the solemnity of the seventh day is very appropriate to this place.