When he had made an end of speaking - These first five verses are omitted by the Septuagint. See the notes on the preceding chapter, 1 Samuel 17 (note).

Jonathan loved him as his own soul - The most intimate friendship subsisted between them; and they loved each other with pure hearts fervently. No love was lost between them; each was worthy of the other. They had a friendship which could not be affected with changes or chances, and which exemplified all that the ancients have said on the subject; Την φιλιαν ισοτητα ειναι, και μιαν ψυχην, τον φιλον ἑτερον αυτον; "Friendship produces an entire sameness; it is one soul in two bodies: a friend is another self."

took him

1 Samuel 16:21-23 And David came to Saul, and stood before him: and he loved him greatly; and he became his armor bearer...

1 Samuel 17:15 But David went and returned from Saul to feed his father's sheep at Bethlehem.

The Exile.
David's first years at the court of Saul in Gibeah do not appear to have produced any psalms which still survive. "The sweetest songs are those Which tell of saddest thought." It was natural, then, that a period full of novelty and of prosperous activity, very unlike the quiet days at Bethlehem, should rather accumulate materials for future use than be fruitful in actual production. The old life shut to behind him for ever, like some enchanted door in a hill-side, and an unexplored land lay beckoning …
Alexander Maclaren—The Life of David