In the Old Testament, God would sometimes tell His people to build a cairn (a mound of rough stones built as a memorial). He knew that people are forgetful and need reminders.
In Joshua 4, we see an example of this, but we need some background information before we can understand it.
So all the way back to the end of Genesis, the Israelites (God’s people) are living in the land of Egypt. In the beginning of Exodus, the King of Egypt enslaves the Israelites and treats them very harshly. In Exodus 1:14, it says the Egyptians “made their lives bitter with hard labor.” In the following verses, we find out that the king starts having their babies killed and increases their workload. The people can’t handle all that is being done to them and they cry out to God for deliverance.
Then God says, “I have surely seen the affliction of My people who are in Egypt, and have given heed to their cry because of their taskmasters, for I am aware of their sufferings. So I have come down to deliver them from the power of the Egyptians, and to bring them up from that land to a good and spacious land, to a land flowing with milk and honey.” Exodus 3:7-8a
