I researched a little of its history and added a link if you want to know more. If you choose to listen, may you be blessed with God's majesty and presence with full knowledge in your heart that our High King of Heaven loves and protects us always!
The following is found in the video description:
Fire glowed against the visage of St. Patrick as he lit yet another candle in the dark Irish churchyard on Slane Hill. The fire reminded him of Christ, Redeemer and light of his life. Opposite the churchyard was Tara, where resided the pagan High King Lóegaire-- the man who outlawed candles in Ireland. But it was the eve of Easter, 433 A.D. and St. Patrick was determined to glorify God that night. And thus began the hymn. "Therefore, on that day when I was rebuked, as I have just mentioned, I saw in a vision of the night a document before my face, without honour, and meanwhile I heard a divine prophecy, saying to me: 'We have seen with displeasure the face of the chosen one divested of name.' And he did not say 'You have seen with displeasure', but 'We have seen with displeasure' (as if He included Himself) . He said then: 'He who touches you, touches the apple of my eye.'"-- Saint Patrick
This is very true for me, especially with this hymn!
"Sometimes hymn singing invites us to connect with the saints who have gone before. Such is the case with the famous Irish hymn, "Be Thou my vision." The original poem, found in two Irish manuscripts in the library of the Royal Irish Academy, may be dated as early as the 8th century." Reference: https://www.umcdiscipleship.org/resources/history-of-hymns-be-thou-my-vision
Maranatha,
Anna