Joshua 4:5
And Joshua said unto them, Pass over before the ark of the LORD your God into the midst of Jordan, and take ye up every man of you a stone upon his shoulder, according unto the number of the tribes of the children of Israel: And Joshua said unto them, Pass over before the ark of the LORD your God into the midst of Jordan, and take ye up every man of you a stone upon his shoulder, according unto the number of the tribes of the children of Israel:
Joshua commanded twelve chosen men, one from each tribe, to go before the ark into the middle of the Jordan and each lift a stone from the riverbed onto his shoulder. The stones were to be taken from the very spot in the channel where the priests bearing the ark had stood. They were to be carried out to dry land on the western side, to Gilgal, and there set up as a monument. By divine direction they were erected at Gilgal where they would remain in sight.
The twelve stones stood for the tribes of Israel, and those who held this understanding taught that they were built into an altar to honor the covenant God made with Israel at the crossing. They were a memorial of Israel's miraculous passage through the Jordan into the promised land on dry ground, when the waters were cut off before the ark. As such they were memorials of God's dealings, mighty power, and deliverance. They were set up to preserve the memory of the event so that later generations would hear how God had brought Israel across and know His power. When children should ask what the stones meant, parents were to repeat the story, teaching how God delivered Israel and making known His power. In this way the stones would strengthen faith and keep His providential care, goodness, mercy, and deliverance alive in memory.