I agree.
With my kids, on the second request I will say “we have already discussed this and the answer is ‘no’. I will not discuss it further”. Then I ignore them. (mind you, I’m not totally consistant… sigh)
Also watch… as they get older, they will try the “ask the other parent” trick…
In your example, you said he is in bed…. with that, he may also just be trying to get attention, so any further talking to him is giving him something he wants….