There appear to be two ways in which the repetition of seven has been understood. In the Bible, seven is often used as a number signifying totality, completion, and perfection. As such, it is used in Joshua 6:1–27 to emphasize the completeness of the Lord’s victory on Israel’s behalf.1
Alternatively, the six-plus-one pattern recalls creation’s seventh day. After six days of creation, the Lord rested on the seventh day and made it holy (Genesis 2:1–3). That is, the seventh day was consecrated to the Lord.2 Marching around the city for seven days and seven times on the final day thus emphasizes that the city of Jericho is consecrated (belongs) to the Lord.
6 So Joshua the son of Nun called the priests and said to them, “Take up the ark of the covenant and let seven priests bear seven trumpets of rams’ horns before the ark of the LORD.”