IMO, no.
I'd agree there were no denominations until the Roman Empire created the Roman Church for itself, but that doesn't make them "bad" (much less "sin").
Christians are not commanded to do so, but often they gather/associate together in a certain place and time often for the purposes of mutual fellowship, support, cooperation, edification, ministry/service, accountability and worship. These are technically called "congregations" (although they may be called "churches" in a sense different than the one, holy, catholic Church - the communion of believers." There are now literally millions of these. While not commanded to do, in time congregations gathered/associated together often for the purposes of mutual fellowship, support, cooperation, education, ministry/service and accountability. These are technically called "denominations."
I don't regard congregations OR denominations to be required. On the other hand, I don't find them forbidden. Indeed, I think they can be very beneficial and a good thing. There are independent, autonomous, "stand alone" Christians who truely believe but aren't a part of any congregation.... and independent, autonomous, "stand alone" congregations that simply aren't a part of any denomination (or anything other than our beyond itself), these are known as "non-denominational" congregations.
MY perspective....
- Josiah
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