Charles Spurgeon Commentary 1 Samuel 18:2-4

"And Saul took him that day, and would let him go no more home to his father`s house. Then Jonathan and David made a covenant, because he loved him as his own soul. And Jonathan stripped himself of the robe that was upon him, and gave it to David, and his apparel, even to his sword, and to his bow, and to his girdle." — 1 Samuel 18:2-4 (ASV)

And Saul took him that day, and would let him go no more home to his father's house. Then Jonathan and David made a covenant, because he loved him as his own soul. And Jonathan stripped himself of the robe that was upon him,

No doubt, one suitable to his rank as the heir apparent to the throne of Israel.