Supervisor thinks his instruction is above what the manuals say

I regularly take all my mail to the street. Even on Saturday. I have a 50/50 business and residential route. Some of the businesses may be closed on Saturday but I take the mail out in case they are open.

Supervisor's instruction: leave business closed mail in the case. Me: I don't think that's right, can you show me where it says that? Supervisor: just follow the instruction.

Does anybody know contractual wording in any manual to support my side or his?

His instruction followed to the letter would mean I also pull out the dps for these businesses?

That makes no sense to me. I'm not endorsing mail business closed or deciding to not deliver mail based on circumstance when I haven't taken the mail to the street to verify the reason the actual circumstance for why the mail is undeliverable today.

Any help is much appreciated. Thank you.