After you read this, go tell your child to do something that sounds absolutely ridiculous. Like, “Put a pair of socks on your ears.” Or, “Sing ‘Happy Birthday’ into the mailbox.” Or, “Go turn all of the door knobs in the entire house.”
If he asks you, “Why?”, don’t indulge him. Just insist he obey without delay.
Then, if he does so, reward him. Give him a piece of chocolate or a sticker or a delayed bedtime.
It’s important that our kids don’t always have a reason for obeying. With my most-likely-to-argue child, I often give him random instructions. And then, when he argues with me, (he usually does) I say, “We’re going to try that again.” And then I repeat the instruction until he complies cheerfully.
It’s good practice for when he has to follow a law or a boss or even the Lord, when it doesn’t seem reasonable. It’s my job to help get him ready.