This does not mean that Solomon becomes an actual son of God, but it describes the personal relationship that he and God will have. AT: "I have chosen to treat him like a son, and I will be like a father to him" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The word "you" here refers to David. Also, the understood word "committed" may be supplied. AT: "just as you are committed this day" (See: [[rc://en/ta/man/translate/figs-ellipsis]])