The Baptism of Olaf Tryggvason
“AND that thou mayst have no doubt, listen to these tokens: When thou comest to thy ships many of thy people will conspire against thee, and then a battle will follow in which many of thy men will fall, and thou wilt be wounded almost to death, and carried upon a shield to thy ship; yet after seven days thou shalt be well of thy wounds, and immediately thou shalt let thyself be baptized.”
Soon after Olaf went down to his ships, where he met some mutineers and people who would destroy him and his men. A fight took place, and the result was what the hermit had predicted, that Olaf was wounded, and carried upon a shield to his ship, and that his wound was healed in seven days.
Then Olaf perceived that the man had spoken truth, and had the gift of prophecy, and he and all his followers were baptized forthwith. He remained here a long time, took the true faith, and got with him priests and other learned men.*
tr. Samuel Laing (abridged)
This was in 988. Sturluson says that Olaf now went to England in peace, as it was a Christian country, and that he married an Irish princess. The Anglo-Saxon Chronicle however indicates that Olaf had not quite done with his career of violence in England: he had to be bought off in 994. See The Oath of Olaf Tryggvason.