Musar zu Schemot 13:22

I will copy from the Tziyoni, who describes these flags in still greater detail: It is a tradition going back to Moses that in addition to the images mentioned on these four flags they also contained one letter each of the names of the three patriarchs, as well as three צירופים, permutations of the letters in the Ineffable Name. Reuben's flag contained the letter ב of Abraham's name, the letter צ of Isaac's name, and the letter ע of Jacob's name. To these letters were added 3 permutations of the letters in the Ineffable Name, such as heh-vav-heh-yud, heh-vav-yud-heh, and heh-heh-yud vav. The flag of Yehudah would have the letters "א", "י", "י", respectively, taken from the names of the patriarchs. To this would be added three more צירופים. When you continue in this fashion, namely the letters "ר", "ח", "ק" from the patriarchs' names on the flag of Ephrayim, with the respective permutations of the Ineffable Name added, and the letters "מ", "ק", "ב" from the patriarchs' names on the flag of Dan, again with the respective unused permutations in the letters of the Ineffable Name, you will remain with the last letter in Abraham's name, i.e. the letter "ה" unaccounted for. In order to solve this problem, G–d added the letter yud, so as to produce the two-lettered name of G–d, the one with which He created the universe, i.e. “י-ה”. G–d placed עמודים, a type of cloud (like the pillar of fire in Exodus 13,22) above, and ענן, another type of cloud, above and below the holy ark. These two letters were engraved on those two clouds. Whenever G–d wanted the camps to move, the columns of cloud containing the letters would rise from the ark, and the four ענני הכבוד, clouds depicting the Presence of G–d's glory on which the letters א-י-י, ב-צ-ע, ר-ח-ק, מ-ק-ב, were inscribed would start moving. So far the Tziyoni.