Midrash Shmuel on David the Pious Warrior and His Wars

"According to all these words, and according to all this vision (so did Nathan speak unto David)" (2 Samuel 7:17). "Then You spoke in vision to Your pious ones, etc." (Psalms 89:20) — this speaks of David, for it was spoken with him in speech and in vision, as it is said, "According to all these words and according to all this vision, so did Nathan speak unto David." "To Your pious ones (la-chasidekha)" — as it is written concerning him, "Keep my soul, for I am pious (chasid)" (Psalms 86:2). "And You said: I have set help upon one that is mighty" (Psalms 89:20). Rabbi Abba bar Kahana said: David made thirteen wars; and the Rabbis say eighteen. And they do not disagree: the one who says thirteen — for the needs of Israel; and the one who says eighteen — five for his own need and thirteen for the needs of Israel. "I have exalted one chosen out of the people" (Psalms 89:20) — [this is David, as it is said,] "And He chose David His servant, etc." (Psalms 78:70).