Whereupon he promised with an oath,.... On account of her fine dancing, and being extremely pleased with it himself; and the more, that it gave such pleasure to the whole court: he first promised her,to give her whatsoever she would ask; and then repeating it, he confirmed it with an oath; adding, as Mark says, that he would give it her, even "to the half of his kingdom": a way of speaking used by princes, when they give full power to persons to ask what they will of them; and to express their great munificence and liberality; signifying, let it be ever so great, or cost what it will, though as much as half a kingdom comes to, it shall be granted; see Es 5:3.
A very foolish promise, and a rash oath these, which were made upon such a consideration, as only a fine dance. If she, as Theophylact observes, had asked for his head, would he have given it her? And if he swore by his head, which was a common form of swearing with the Jews , she very appropriately, though unjustly, as Dr.
Lightfoot observes, answers to him; as you have swore by your head, give me John Baptist's head. Misn. Sanhedrim, c. 3. sect 2. T. Bab. Beracot, fol. 3. 1. Derech Eretz, c. 6. fol. 18.