John Gill Commentary 2 Samuel 15:16

"And the king went forth, and all his household after him. And the king left ten women, that were concubines, to keep the house." — 2 Samuel 15:16 (ASV)

And the king went forth
Which determined the case:

and all his household after him family and his court ;
they followed his example, and attended him in his flight:

and the king left ten women, [which were] concubines, to keep the
house ;
not to defend it, which they were unable to do, but to look after the household goods and furniture, that they were not damaged by the conspirators; though one would think they could be of little service, and may wonder what he should leave them behind for; but this seems to be ordered by the overruling providence of God, to bring about what was threatened him, (2 Samuel 12:11) ; and it is much he had not thought of it; but it was hid from his eyes, that it might be fulfilled.