(20) The firstling of an ass.--See Notes 1-3 on Exodus 13:13.

34:18-27 Once a week they must rest, even in ploughing time, and in harvest. All worldly business must give way to that holy rest; even harvest work will prosper the better, for the religious observance of the sabbath day in harvest time. We must show that we prefer our communion with God, and our duty to him, before the business or the joy of harvest. Thrice a year they must appear before the Lord God, the God of Israel. Canaan was a desirable land, and the neighbouring nations were greedy; yet God says, They shall not desire it. Let us check all sinful desires against God and his glory, in our hearts, and then trust him to check all sinful desires in the hearts of others against us. The way of duty is the way of safety. Those who venture for him never lose by him. Three feasts are here mentioned: 1. The Passover, in remembrance of the deliverance out of Egypt. 2. The feast of weeks, or the feast of Pentecost; added to it is the law of the first-fruits. 3. The feast of in-gathering, or the feast of Tabernacles. Moses is to write these words, that the people might know them better. We can never be enough thankful to God for the written word. God would make a covenant with Israel, in Moses as a mediator. Thus the covenant of grace is made with believers through Christ.Every firstling of an ass thou shalt redeem,.... This goes along with the former; see Gill on Exodus 13:13,

and none shall appear before me empty; at the grand festivals, the passover, pentecost, and tabernacles; see Gill on Exodus 13:15.