When it is seen - When it occurs; that is, when Moab actually “becomes” weary.
Is weary on the high place - The “high place” denotes the place of idolatrous worship, and here means the same as the temple of Chemosh or his sanctuary. Temples and altars were usually constructed on such places, and especially the temples of the pagan gods. Moab is represented here as looking to her gods for protection. Weary, exhausted, worn down with calamities, she is represented as fleeing from the desolate towns and cities, and taking refuge at the altar, and seeking assistance there. This, says Jerome, is the final misery. She is now forsaken of those aids to which she had always trusted, and on which she had relied. Her people slain; her towns destroyed; her strong places broken down; her once fertile fields languishing and desolate, she flees to the shrine of her god, and finds even her god unable to aid and defend her.
Shall come to his sanctuary - To his “principle” sanctuary; or to the temple of the principal god which they worshipped - the god “Chemosh” 1 Kings 11:7. This does not mean the temple at Jerusalem, though Kimchi so understands it; but the temple of the chief divinity of Moab. Jerome says that this temple was on mount Nebo.
Shall not prevail - That is, her prayer shall not be heard.