The song is known as "The Son of God Goes Forth To War" or "Bishop Heber's Hymn" The melody is "The Moreen" which is commonly known as "The Minstral Boy". The words are sung as Danny Dravot (Connery) walks out on the bridge before he falls to his death.

The son of God goes forth to war a kingly crown to gain,

His blood red banner streams afar, who follows in his train,

The words can be found in The Heart Songs book.

Don