It was reported to Solomon: “Behold, Adonijah fears King Solomon, and he has taken hold of the horns of the altar, saying, ‘Let King Solomon first swear to me not to put his servant to the sword.’”
Jewish Publication Society of America Version (JPS1917) - 1 Kings 1:51 >And it was told Solomon, saying: 'Behold, Adonijah feareth king Solomon; for, lo, he hath laid hold on the horns of the altar, saying: Let king Solomon swear unto me first of all that he will not slay his servant with the sword.'