What are the proofs and foundations for the view that it is permissible to act upon a certificate obtained through fraud, if its owner repents and is proficient in his work?

Cheating is forbidden, for the Prophet, peace and blessings be upon him, said: "Whoever cheats is not of me." The one who cheats must repent to Allah. There is no harm in working with a certificate obtained through cheating if its holder performs his work well, because the intention is competence for the work, and the certificate is considered an indication of that. The person's repentance magnifies the concession, for whoever repents, what has passed is his, as stated in the verse: "So whoever receives an admonition from his Lord and desists, he may have what has passed, and his affair is [left] to Allah." This is completely different from a forged certificate.