John Gill Commentary 1 Kings 1:3

"So they sought for a fair damsel throughout all the borders of Israel, and found Abishag the Shunammite, and brought her to the king." — 1 Kings 1:3 (ASV)

So they sought for a fair damsel throughout all the coasts of
Israel
Not only a damsel, but a beautiful one, that she might be the more acceptable to the king; who otherwise, if deformed and ugly, would not have endured her in his sight, or received at her hands, and much less suffered her to lie in his bosom:

and found Abishag a Shunammite ;
a native of the city Shunem, a city in the tribe of Issachar, (Joshua 19:18) ;

and brought her to the king ;
for his approbation of her, and to make her his concubine wife, as he did.