John Gill Commentary 1 Kings 1:11

"Then Nathan spake unto Bath-sheba the mother of Solomon, saying, Hast thou not heard that Adonijah the son of Haggith doth reign, and David our lord knoweth it not?" — 1 Kings 1:11 (ASV)

Wherefore Nathan spoke unto Bathsheba the mother of Solomon ,
&c.] Who not only had an interest in the king, being his wife, and an easy access to him, but had a special concern in this affair, as it affected her son, to whom the succession of the kingdom was designed and promised:

saying, have you not heard that Adonijah the son of Haggith does
reign ?
has usurped the throne, and is proclaimed king by a party, who at least have drank his health as such; has taken the title, and is about to exercise the power of a king; this Bathsheba might not have heard of, and which he expresses in this manner to quicken her to make an immediate application to the king:

and David our Lord knows [it] not ;
being so infirm, and in his bed, and nobody about him to inform him of it; it was done without his knowledge, and far from being with his consent and approbation.