Swearing is sacred(my opinion)

So look.. I understand it’s a sin to swear, but I kinda need your help.

Let’s say a person does tell the truth when he swears and puts it on family or worse on Jesus Name. Does it also count as a swear if I tell him “Put it on your father(as it’s very important for him) or your life” because I know he typically tells the truth when he does that.
But his response is just “Yeah bro, just say what you want..”. Is it still swearing on something?

There are people that do it without any sense, but I really trust and can somehow know if he does lie, and just wanted to know how to take it because it’s context it’s deeper and complicated to read him.

Does he tell the truth or not?