And those twelve stones, which they took out of Jordan, did Joshua pitch in Gilgal.

Wesley's Notes

4:20 In Gilgal - Probably in order, like so many little pillars, to keep up the remembrance of this miraculous benefit.

Jamieson-Fausset-Brown Bible Commentary

20-24. those twelve stones, which they took out of Jordan, did Joshua pitch in Gilgal-Probably to render them more conspicuous, they might be raised on a foundation of earth or turf. The pile was designed to serve a double purpose-that of impressing the heathen with a sense of the omnipotence of God, while at the same time it would teach an important lesson in religion to the young and rising Israelites in after ages.

Matthew Henry's Concise Commentary

4:20-24 It is the duty of parents to tell their children betimes of the words and works of God, that they may be trained up in the way they should go. In all the instruction parents give their children, they should teach them to fear God. Serious godliness is the best learning. Are we not called, as much as the Israelites, to praise the loving-kindness of our God? Shall we not raise a pillar to our God, who has brought us through dangers and distresses in so wonderful a way? For hitherto the Lord hath helped us, as much as he did his saints of old. How great the stupidity and ingratitude of men, who perceive not His hand, and will not acknowledge his goodness, in their frequent deliverances!