What is the wisdom behind the Prophet's—peace and blessings be upon him—stoning of the married fornicator, despite the absence of explicit evidence for stoning in the Holy Quran?

Allah commanded stoning (rajm) and revealed a Quranic verse concerning it, whose wording was abrogated but its ruling remained. The Prophet's (peace be upon him) application of stoning was an implementation of Allah's command. The Qur'an is not the sole source of legislation; what the Prophet did, commanded, or forbade is also considered legislation. The wisdom behind the legitimacy of stoning, and not merely doubling the lashing, is that this is Allah's judgment, and there is no better judgment than His. One must submit to it, even if the wisdom is not apparent.