Deuteronomy 22:12

You shall make you fringes (tassels) on the four quarters of your clothing, with which you cover yourself.

גְּדִלִים ~ tassels ~ gedil ~ twisted threads

Numbers 15:38-39

And the LORD spoke to Moses, saying, Speak to the children of Israel, and bid them that they make them fringes in the borders of their garments throughout their generations, and that they put on the fringe of the borders a ribbon of blue: And it shall be to you for a fringe, that you may look on it, and remember all the commandments of the LORD, and do them; and that you seek not after your own heart and your own eyes, after which you used to go a whoring: That you may remember, and do all my commandments, and be holy to your God.

For Elli's undershirts, I simply attached the tassels with a thread of cotton where the four corners meet. There is no set way they have to be tied, but they must contain a cord of blue and from my understanding of the Hebrew word for tassels (gedil) which means twisted thread, that maybe the threads should be twisted (braided or knotted?) together. But, we have much freedom to walk out His ways with creativity!

The children of Israel needed a physical reminder.  But I wasn't sure that we NEED tassels as a physical reminder today because YHVH writes His laws on our hearts and minds (Hebrews 8:10), helping us to remember all of His commands. (John 14:26).

"But the helper, the Set-apart Spirit, whom the Father shall send in My Name, He shall teach you all, and remind you of all that I said to you." 

However, I remembered that we still remove the leaven from our home, which is a physical reminder of spiritual things, so yes, we still do need a physical reminder! We need all the help we can get, haha!