Charles Ellicott Commentary 2 Samuel 19:24

"And Mephibosheth the son of Saul came down to meet the king; and he had neither dressed his feet, nor trimmed his beard, nor washed his clothes, from the day the king departed until the day he came home in peace." — 2 Samuel 19:24 (ASV)

Came down to meet. — The obvious meaning of this is that Mephibosheth came down from the high land of Jerusalem to meet the king in the Jordan valley. In this case, the following verse should be translated: And it came to pass when Jerusalem (meaning its inhabitants, with Mephibosheth among them) was come to meet the king.

Some writers, however, prefer to keep 2 Samuel 19:25 as it is. They suppose that during the rebellion Mephibosheth had taken refuge on his ancestral estate near the heights of Gibeah, and that he came from there to Jerusalem to meet David.

In either case, the signs of deep mourning Mephibosheth displayed from the day the king departed were evidence of his loyalty. The word for beard is used only for the moustache.