Lyrics: Attributed to Saint Dallon Fargaill (6th century)
Translated to English by Mary E. Byrne (1905)
Versified by Eleanor Hull (1912)

Music: Irish folk melody, SLANE.

Theme:
After this, the word of the LORD came to Abram in a vision: “Do not be afraid, Abram. I am your shield, your very great reward.” Genesis 15:1.

For the LORD gives wisdom, and from his mouth come knowledge and understanding. Proverbs 2:10

And there before me was the glory of the God of Israel, as in the vision I had seen in the plain. Ezekiel 8:4.

And afterward, I will pour out my Spirit on all people. Your sons and daughters will prophesy, your old men will dream dreams, your young men will see visions. Joel 2:28.

I keep asking that the God of our Lord Jesus Christ, the glorious Father, may give you the Spirit of wisdom and revelation, so that you may know him better. Ephesians 1:17.

David Nevue, piano arrangement:

Listen to this hymn in Gaelic:

Eleanor M. Hull, in her 1912 Poem Book of the Gael wrote this poetic translation of the old Irish hymn dating back to the eighth, perhaps the sixth, century:

Be Thou my Vision, O Lord of my heart;
Naught be all else to me, save that Thou art.
Thou my best Thought, by day or by night,
Waking or sleeping, Thy presence my light.

Be Thou my Wisdom, and Thou my true Word;
I ever with Thee and Thou with me, Lord;
Thou my great Father, I Thy true son;
Thou in me dwelling, and I with Thee one.

Be Thou my battle Shield, Sword for the fight;
Be Thou my Dignity, Thou my Delight;
Thou my soul’s Shelter, Thou my high Tower:
Raise Thou me heavenward, O Power of my power.

Riches I heed not, nor man’s empty praise,
Thou mine Inheritance, now and always:
Thou and Thou only, first in my heart,
High King of Heaven, my Treasure Thou art.

High King of Heaven, my victory won,
May I reach Heaven’s joys, O bright Heaven’s Sun!
Heart of my own heart, whatever befall,
Still be my Vision, O Ruler of all.

Patrick Joyce published the traditional Irish tune Slane, named for a hill near Tara where St. Patrick challenged the druid priests in lighting the paschal fire. Hull’s words and the traditional tune were paired in the Irish Church Hymnal in 1919, and lo, we have Be Thou My Vision, a reminder of the vision of Celtic Christianity and the baptized imagination of medieval Celtic Christians who saw God as the mighty High King of Heaven, ruling over all things and at the same time immanent and intimately present in our lives.

Popular Hymns.com: Desktop Backgrounds for Be Thou My Vision.

Sources;
Christianity Today Library: Be Thou My Vision.