All that openeth the matrix is mine,.... Or "the womb", and therefore to be sanctified, and set apart for his use: this also was declared, and the law concerning it given, at the time of their coming out of Egypt, and here repeated; see Gill on Exodus 13:2, Exodus 13:12.

All that openeth the matrix is mine; and every firstling among thy cattle, whether ox or sheep, that is male.

sheep: or, kid

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.