"Saint Patrick's Breastplate" is a hymn whose original Old Irish lyrics were traditionally attributed to Saint Patrick and his Irish ministry in the 5th century. It is written in the style of a druidic incantation for protection on a journey.
The words were translated into English verse by Cecil Frances Alexander in 1889 and set to two traditional Irish tunes, "St. Patrick" and "Deirdre". The hymn, also known by its opening line "I bind unto myself today", is currently included in the many modern-day church hymnals.
It is often sung during the celebration of the Feast of Saint Patrick on or near March 17, as well as on Trinity Sunday. In many churches, it is unique among hymns because the variations in length and metre of verses mean that at least three different tunes must be used.
The prayer is also known as "Faeth Fiada" or the "Lorica of St. Patrick" (St. Patrick's Breast-Plate).
Check out this YouTube beautifully sung by Angelina. You can download a copy of the hymn by clicking on the PDF attached to this news article.