1 Kings 2:28

28 When the news reached Joab, who had conspired with Adonijah though not with Absalom, he fled to the tent of the LORD and took hold of the horns of the altar.

Read 1 Kings 2:28 Using Other Translations

Then tidings came to Joab: for Joab had turned after Adonijah, though he turned not after Absalom. And Joab fled unto the tabernacle of the LORD, and caught hold on the horns of the altar.
When the news came to Joab--for Joab had supported Adonijah although he had not supported Absalom--Joab fled to the tent of the LORD and caught hold of the horns of the altar.
Joab had not joined Absalom’s earlier rebellion, but he had joined Adonijah’s rebellion. So when Joab heard about Adonijah’s death, he ran to the sacred tent of the LORD and grabbed on to the horns of the altar.