How much do you know of his background?
My exh husband lied all the time and it was the main contributing factor to the breakdown of our marriage. I didn't realise some of the lies until after we'd separated. Some of them were big and some of them were utterly pointless. It got to the point where, if asked him if he wanted a cup of tea, I couldn't trust his answer!
He did it for two reasons. The main one being that his parents were both alcoholics and anyone who has lived with alcoholic parents will know that it's a survival strategy.
The other was that his parents' relationship was toxic and littered with aggressive arguments and violence (in both directions).
He knew he didn't want to be like them so wasn't but what he fashioned himself into was equally dysfunctional and he believed in the mantra of happy wife, happy life and so just lied. He told me once that he believed that if he told me what (he thought) I wanted to hear, I'd be happy so he'd be happy. He didn't understand honesty or partnership at all.
I wouldn't be in a relationship with a liar again because the problem is it becomes like the house built on sand or rock. Your house can only ever be built on sand and you cannot trust a single word they say about anything because you never know what is a lie or whether you're ever hearing the truth.
It got to the point where I couldn't be bothered talking to him about anything. Even what we were going to have for dinner or where we were going to go on holiday because the responses were never honest.
He's now remarried and I know he lies to her too.
It's a trauma response. Even being asked a simple innocuous question triggers a fight, flight, freeze or fawn response in him so I guess he fawns - hence the lies.
But it's very damaging to be around.