This song is widely considered to be about Van Morrison's relationship with God and religious convictions. Although we've never heard him speak specifically about the song, he does acknowledge a spiritual element in his music. When asked about the topic in a 2009 Q&A in Time magazine, Morrison said, "Religion is a kind of word game. It's whatever it means to those individuals who are following that belief system. If you say something has got spirit or "I feel the spirit," to me, that would be more appropriate - spirit in the Aristotelian sense, that the mind and body and spirit are one thing. Which is different from religion."
Rod Stewart performed this on his MTV Unplugged special in 1993 and released this acoustic version on his album Unplugged... And Seated. This version was a big hit, going to #5 in both the US and UK. Stewart cried at the end of his MTV performance, overcome with emotion for his wife at the time, actress and swimsuit model Rachel Hunter. They were married from 1990-1999. Hunter claimed after the divorce that Rod "got boring."
There is a Country song from the '40s called "Have I Told You Lately That I Love You," which was recorded by Elvis Presley, Gene Autry, Bing Crosby and Ray Price, but that's a completely different song. That one was written by Scotty Wiseman.
Morrison recorded this song with The Chieftans in 1995. This version appeared on the group's album The Long Black Veil and earned a Grammy for Best Pop Collaboration with Vocals.