From "Game of Thrones: Oathkeeper (#4.4)"
Your brother ever tell you how I came into his service?
You stood for him in his trial by combat at the Eyrie.
Aye. But only when Lady Arryn demanded the trial take place that day. You were his first choice. He named you for his champion because he knew you would ride, day and night, to come fight for him. You gonna fight for him now?