Psalms 81:1

When the people of God were gathered together in the solemn day, the day of the feast of the Lord, they must be told that they had business to do, for we do not go to church to sleep nor to be idle; no, there is that which the duty of every day requires, work of the day, which is to be done in its day. And here, I. The worshippers of God are excited to their work, and are taught, by singing this psalm, to stir up both themselves and one another to it, Psa 81:1-3. Our errand is, to give unto God the glory due unto his name, and in all our religious assemblies we must mind this as our business. 1. In doing this we must eye God as our strength, and as the God of Jacob, Psa 81:1. He is the strength of Israel, as a people; for he is a God in covenant with them, who will powerfully protect, support, and deliver them, who fights their battles and makes them do valiantly and victoriously. He is the strength of every Israelite; by his grace we are enabled to go through all our services, sufferings, and conflicts; and to him, as our strength, we must pray, and we must sing praise to him as the God of all the wrestling seed of Jacob, with whom we have a spiritual communion. 2. We must do this by all the expressions of holy joy and triumph.

— Matthew Henry's Concise Commentary (public domain)