Adam Clarke on 2 Kings 19:37

Nisroch his god - We know nothing of this deity; he is nowhere else mentioned.

Smote him with the sword - The rabbins say that his sons had learned that he intended to sacrifice them to this god, and that they could only prevent this by slaying him.

The same writers add, that he consulted his wise men how it was that such miracles should be wrought for the Israelites; who told him that it was because of the merit of Abraham who had offered his only son to God: he then said, I will offer to him my two sons; which when they heard, they rose up and slew him. When a rabbin cannot untie a knot, he feels neither scruple nor difficulty to cut it.