For this was a statute for Israel, and a law of the God of Jacob.

Matthew Henry's Concise Commentary

81:1-7 All the worship we can render to the Lord is beneath his excellences, and our obligations to him, especially in our redemption from sin and wrath. What God had done on Israel's behalf, was kept in remembrance by public solemnities. To make a deliverance appear more gracious, more glorious, it is good to observe all that makes the trouble we are delivered from appear more grievous. We ought never to forget the base and ruinous drudgery to which Satan, our oppressor, brought us. But when, in distress of conscience, we are led to cry for deliverance, the Lord answers our prayers, and sets us at liberty. Convictions of sin, and trials by affliction, prove his regard to his people. If the Jews, on their solemn feast-days, were thus to call to mind their redemption out of Egypt, much more ought we, on the Christian sabbath, to call to mind a more glorious redemption, wrought out for us by our Lord Jesus Christ, from worse bondage.