It seems a lot of the songs I don’t know already from GA have a text by Shirley Erena Murray. She wrote this wedding song that is set to BUNESSAN. It is a great idea to use a familiar hymn tune to encourage participation at a liturgy where people of all faiths and none will attend, like a wedding. Most people will recognise this tune quickly.
You can find the text and sheet music from the wonderful people at Hope Publications.