There is some evidence that the Torah intended the idea of tefillin (totafot in the Shema, sometimes translated as “phylacteries”) metaphorically. Inner biblical exegesis — comparison with other parts of the Bible — gives us an insight into this.
Take these verses for example: “My son, keep your father’s commandment. Do not forsake your mother’s teaching.
“Tie them over your heart always. Bind them around your throat.
“When you walk it will lead you. When you lie down it will watch over you. And when you are awake it will talk with you” (Proverbs 6:20-22)