Activation lock

See Turn off Activation Lock https://support.apple.com/en-us/HT201441 See this heading If you erased your own device.

Did you erase your phone without signing out of iCloud first? If yes, and you can't recover your credentials, you'll need to have your receipt for the phone with it serial number on it and contact Apple support. Use these support options:

Get a call from Apple support to help solve your problem using this link https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362

Apple ID Support https://support.apple.com/apple-id

Apple ID account security for country-specific and region-specific help https://support.apple.com/en-us/HT204169

Get Support: We’re here to help  https://getsupport.apple.com/. Go through the options to find the best support option.

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Otherwise, the phone is useless to you.

Send him the links I posted above. If he isn't able to get back into that Apple ID and doesn't have the purchase receipt, he won't be able to activate the iPhone; the activation lock is an anti-theft measure.

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Use Apple's iForgot service, or contact their Account Security team, or if you’re the iPhone’s original owner, supply Apple with its purchase receipt and ask them to remove the lock.

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