What is the legal basis for the validity of confession (Iqrar)?

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Confession is legally sound based upon the Quran, the Sunnah, and consensus (Ijma). Evidence from the Quran includes verses where God took the covenant of the Prophets (Quran 3:81), verses mentioning those who confessed their sins (Quran 9:102), and the confirmation of God's Lordship (Quran 7:172), among others. The Sunnah is established by the report that the Prophet (peace be upon him) executed Ma'iz and the Ghumadiyyah woman based on their confessions of Zina (adultery/fornication). Furthermore, the report commanding Anis to check if the woman confessed before executing the prescribed punishment confirms the validity of confession. Consensus exists among the Ummah regarding the correctness of a confession. A confession is considered the strongest form of testimony because a rational person would not lie about something detrimental to themselves; thus, if the defendant confesses, no testimony against him is heard, unlike when he denies.