1 Kings 1:51

“And it was told Solomon, etc.] By some of his courtiers: saying, behold, Adonijah feareth King Solomon; lest he should take away his life: for, lo, he hath caught hold on the horns of the altar; which was the last resort of the guilty when they despaired of mercy otherwise: saying, let King Solomon swear unto me this day that he will not slay his servant with the sword; he owns Solomon to be king, and himself his subject and servant; this no doubt he did to conciliate his favour, nor did he think his life safe, unless Solomon promised with an oath, that he would not take it away.”

“His servants - He owns Solomon as his king, and himself as his servant and subject; and being sensible of his guilt, and of the jealousy which kings have of their competitors, could not be satisfied without Solomon's oath. 3 Kings (1 Kings) 1:53”

“When this was reported to Solomon, together with the prayer of Adonijah that the king would swear to him that he would not put him to death with the sword (אם before ימית, a particle used in an oath), he promised him conditional impunity: "If he shall be brave (בּן־חיל, vir probus), none of his hair shall fall to the earth," equivalent to not a hair of his head shall be injured (cf. Sa1 14:45); "but if evil be found in him," i.e., if he render himself guilty of a fresh crime, "he shall die." 3 Kings (1 Kings) 1:53”