Adam Clarke on 1 Kings 1:50

Adonijah feared - He knew he had usurped the kingdom, and had not his father's consent; and, as he finds now that Solomon is appointed by David, he knows well that the people will immediately respect that appointment, and that his case is hopeless; he therefore took sanctuary, and, fleeing to the tabernacle, laid hold on one of the horns of the altar, as if appealing to the protection of God against the violence of men. The altar was a privileged place, and it was deemed sacrilege to molest a man who had taken refuge there. See 1Kgs 2:28.