What constitutes a marriage in God’s eyes?

I have seen this question a lot and several different answers, but what do yall think?

Personally, it seems like it’s mainly just the covenant between you and God with vows and witnesses (preferably with an ordained minister).

But some people say you HAVE to have legal documentation. Which, while it IS helpful, I’m not sure why God would care if you were legally married as it changes nothing other than government recognition and some benefits?

What do yall think?