Numbers 15:39-40 And it shall be unto you for a fringe, that ye may look upon it, and remember all the commandments of the Lord and do them; and that ye seek not after your own heart and your own eyes, after which ye use to go a-whoring: that ye may remember to do all my commandments, and be holy unto your God.
The people were to respond to the Lord’s Covenant of Salvation by making fringes of blue ribbons on the borders of their clothes. The purpose was that they would see it and be reminded of whom they belonged to, and remember all the Commandments of the Lord and do them.
The fringe itself had no inherent value or power, like a charm, but God gave it meaning: wear it as a reminder of Me. The distractions of the world are so prevalent and powerful that we will surely, not just likely, go whoring after the world’s gods. We should not be so pridefully arrogant that we don’t think we need reminders. We don’t need special clothing or cross jewelry, but we do need a regular dose of Word and Sacrament to remember our God, His grace, His salvation, and His presence. These constant gospel reminders effectively move us to do the Law and live a godly life.
In actual practice, a Christian may employ any physical object as a reminder of the Gospel Promise, who God is, and what He has done for us. And we go to church to keep on the path and not be led astray.