Therefore we said, Let us now prepare to build us an altar, not for burnt offering, nor for sacrifice:

Matthew Henry's Concise Commentary

22:21-29 The tribes took the reproofs of their brethren in good part. With solemnity and meekness they proceeded to give all the satisfaction in their power. Reverence of God is expressed in the form of their appeal. This brief confession of faith would remove their brethren's suspicion that they intended to worship other gods. Let us always speak of God with seriousness, and mention his name with a solemn pause. Those who make appeals to Heaven with a careless God knows, take his name in vain: it is very unlike this. They express great confidence of their own uprightness in the matter of their appeal. God knows it, for he is perfectly acquainted with the thoughts and intents of the heart. In every thing we do in religion, it highly concerns us to approve ourselves to God, remembering that he knows the heart. And if our sincerity be known to God, we should study likewise to let others know it by its fruits, especially those who, though they mistake us, show zeal for the glory of God. They disdained the design of which they were suspected to be guilty, and fully explained their true intent in building this altar. Those who have found the comfort and benefit of God's ordinances, cannot but desire to preserve them to their seed, and to use all possible care that their children may be looked upon as having a part in him. Christ is the great Altar that sanctifies every gift; the best evidence of our interest in him is the work of his Spirit in our hearts.