John Gill Commentary Mark 6:23

"And he sware unto her, Whatsoever thou shalt ask of me, I will give it thee, unto the half of my kingdom." — Mark 6:23 (ASV)

And he swore to her
He added an oath to what he had before said, the more to confirm it, and to encourage her in her request, and which he repeated in stronger language:

whatever you ask of me, I will give it you, to the half
of my kingdom; (See Gill on Matthew 14:7).