Santo, Santo, Santo is an Argentine folk song that has become popular in American churches and is included in many different hymnals. It is in the The Faith We Sing (#2007), a supplement to the 1989 United Methodist Hymnal. Here's an audio recording of Santo, Santo, Santo from Hymnary.org.
"Santo, santo, santo.
Mi corazon te adora!
Mi corazon te sabe decir:
Santo eres, Dios!
English singing translation:
"Holy, holy, holy.
My heart, my heart adores you!
My heart knows how to say to you:
You are holy, Lord!"