I love a challenge, so I had a go. The tune is 'Cornwall' (886 886): you can hear it here.
(this post has been edited 6th Aug, to add my thoughts and to change the text of the hymn a bit: thanks to Kathryn and Paul for comments).
My main inspiration - apart from having to fit that tune! - was the wedding service itself. It has always seemed odd to me that we don't have wedding hymns that celebrate the amazing vows that are being made. So as much as possible I have quoted from the wedding service. The first line, 'Unending love and faithfulness' is from the blessing of the rings: it fit the meter perfectly, so I knew I wanted it in there.
'All that I am I give to you, all that I have I share with you' is part of the words the couple say to each other at the exchange of the rings, and has always seemed to me to be the most amazing words any one can promise to another person.
The second verse begins a version of the sentence that opens the wedding service, 'God is love, and those who live in love live in God, and God lives in them'. Apart from being a lovely phrase, it seems particularly helpful and appropriate for use in a context where many at least of the guests, and often one or more of the couple, are a little agnostic about their faith: it helpfully explains God in terms of the love that everyone is there to celebrate, and assures everyone that they can speak of God in this context with a clear conscience.
I was also very conscious that, whilst this is a commissioned piece and I wanted it to be meaningful for the couple involved to sing, it needed to work sung by the whole congregation. So places where it uses 'our' are deliberately slightly ambiguous, referring both to the couple and to the congregation. And the direct quote from the vows is in inverted commas.
Finally, I was conscious at the back of my mind that I wanted to make sure this could be sung at a same sex commitment ceremony (and indeed by feminists!), so I wanted to focus on celebrating the quality of commitment rather than any particular baggage about what marriage has meant historically.
I don't think this is particularly brilliant poetry, if I'm honest, but it does work better sung to the tune (try it!).
I really enjoyed the challenge...and am inspired to try to write more hymn words for places where the canon seems to have gaps!
Unending love and faithfulness
We sing with heartfelt thankfulness
And celebrate today;
Commitment, comfort, honour, joy
Our hearts and minds and tongues employ
And may our lives display.
For God is love: living in love
We live in God, and God above
Our hearts and lives enfolds.
Family and friends to share our bliss (NB, 'Family' needs to be sung 'Fam'ly'!)
Our joy, our heaven on earth is this (Acknowledgement: this line is from Wesley)
All love this love upholds.
All that I have I share with you”:
These vows fill us with awe.
This promise will be our delight
Our inspiration day and night
From this day evermore.
You're welcome to use these words if you would like to under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported licence.