John Gill Commentary 1 Kings 1:15

"And Bath-sheba went in unto the king into the chamber: and the king was very old; and Abishag the Shunammite was ministering unto the king." — 1 Kings 1:15 (ASV)

And Bathsheba went in unto the king into the chamber
Where he lay, being bedridden; she took Nathan's advice, and directly went to the king's apartment:

and the king was very old :
and decrepit, borne down with the infirmities of old age, though but seventy years of age:

and Abishag the Shunammite ministered unto the king ;
she was then waiting upon the king, and serving him with what was necessary and proper for him; and perhaps there was no other in the chamber at that time.