Sh'mu'el Alef (1 Sa) 18:1-3

By the time David had finished speaking to Sha’ul, Y’honatan found himself inwardly drawn by David’s character, so that Y’honatan loved him as he did himself. That day, Sha’ul took David into his service and would not let him go home to his father’s house any more. Y’honatan made a covenant with David, because he loved him as he did himself.