Commentary for II Samuel 22:51

A tower of salvations of [God's] king. It is possible that when a person contemplates the matter of Bat Sheva, one will see in graduation that that she rises in the ordering of one step higher above one step higher, which is, that, at the beginning, she was not forbidden, but she 'attached' [to David] as the woman [i.e., wife] of David, the servant of the Lord. And, afterwards, Shelomoh [Solomon] was born, and, afterwards, Shelomoh ruled, and, afterwards, God appeared to him and gave him wisdom and knowledge and wealth and kavod ["glory" or "substance"], and, afterwards, he built the Temple. And it is to be found that the enemies of David had said "There is no salvation for him" (Psalm 3:3), except that he had salvation, for [God] was increasingly magnifying in gradations this salvation slowly, slowly, upwards upon upward [steps], and this is what is meant by "[God] magnifies the salvations of God's king," for salvation is fruitful and multiplies, and one [more comes] from one--going up and increasing, and this is [as a result:] many salvations, and a "tower" is made. The ketiv (the Masoretic Text's written tradition) has magdil ("magnifying"), for it was gradual, and we read [aloud] migdol ("a tower") "of salvations."

"A tower." [David] wanted to say: And thusly, I will praise You, for I will recount, saying, "Know that the Lord is a tower [of salvations], etc.." [He] wanted to say: "[God] performs great salvations for [God]'s king, and not for the sake of the payment of a reward but out of lovingkindness.

Migdol of salvations for God's king. That is to say, that that [God] is a stronghold of salvations for God's king, and that [latter] is David, just as a migdal (מגדל, the normative word for 'tower') is a stronghold of a city.