What is the right answer in this case?

There is a newlywed couple where both work (the in-laws never asked for the passcode in the first place) -
One day, the mother-in-law called her son and said, "I made kimchi, and since you two are both working and busy, I'll go there myself and put it in the fridge~" and asked for the passcode -
The son gave her the passcode - After getting home from work, the wife found out and flew into a rage - A couple's fight ensued
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What should the husband have done…