John Gill Commentary 1 Kings 1:4

"And the damsel was very fair; and she cherished the king, and ministered to him; but the king knew her not." — 1 Kings 1:4 (ASV)

And the damsel [was] very fair
And so very agreeable to the king to be in his presence, and wait upon him, and take things of her hand, as well as lie with him:

and cherished the king ;
enlivened his spirits by her amiable countenance, her graceful behaviour, and tender care of him, and especially by bedding with him:

and ministered to him ;
serving him with her own hands whatever he took for his sustenance:

but the king knew her not ;
as a man knows his wife; which shows that she was his wife, and that it would not have been criminal in him had he known her; but this is observed, not to point at the chastity of David, but his feebleness, and loss of desire after women, and that the damsel remained a virgin; and that was the ground of Adonijah's request, and his hope of succeeding.