Rabbi Simcha Weinberg recently posted a shtikl Torah on tzitzit and Chanukah, quoting the Midrash on Tehillim: “Rabbi Meir was wont to say: When a man wears tefillin upon his head and upon his arm, as prescribed, and his four tzitzit enclosing on all four sides, and when as he enters his house there is a mezuzah at the entrance, you find that the Seven Testimonies of his awe of God surround him like a wall.”

This reminds my of how we surround ourselves with mitzvahs on Chanukah: If you light Chanukah candles in the doorway, you are supposed to light them opposite the mezuzah so that you have a mitzvah on either side.

Rabbi Weinberg goes on to note that David Hamelech would hold his tzitzit “surrounding me as a wall to protect me from the enemies who surround me.”