Matthew Poole and continuators on 1 Kings 1:50

50 ¶ And Adonijah feared, because of Solomon, and arose, and went, and caught hold on the horns of the altar .

Either, that which was at Gibeon, as appears from 1 Chron. 16. 39. 2 Chron. 1. 3. and was made with four Horns, Exod. 38. 2. to which the Sacrifices were bound, Psal. 118. 27. Or rather, that which David had lately set up in the Threshing-floor of Araunah, which doubtless was made after the same form as that at Gibeon: For, First, This was next at hand. Secondly, The Altar onely is mentioned here, whereas in Ioab's case there is mention of the Tabernacle and Altar both, Chap. 2. 28, 29. which seems to be noted to distinguish the two Altars: for Adonijah being the Kings Son, he might safely go to Araunah's Altar, and the People would not be forward to seize upon him, or bring him to Justice: but Ioab truly thought it was not safe for him to venture himself there, and therefore he flieth to Gibeon, as a place more remote from Ierusalem. Hither he fled, either to implore Gods Mercy; or rather, to avoid Solomon's Rage; sapposing that his Reverence to that Sacred place would not permit him to pollute it with his Brothers blood; or that the consideration of Gods Grace and Mercy, which himself needed and begged of God, in pardoning his offences, and accepting the Sacrifices which he should offer there, would engage and dispose him to shew Mercy to his offending and now penitent Brother; or, that his Piety would not allow him violently to pluck him as it were out of the Arms of God, into which he had put himself. And for these or such like reasons the Altar was esteemed a kind of Sanctuary or place of Refuge, not onely among the Gentiles, but also among the Hebrews, though it be not called by that name, as may be gathered from Exod. 21. 14. 1 King. 2. 28.