Fitra is the original constitution on which human beings are said to have been created, an innate disposition toward recognising the one God. Its verse is 30:30: "So set your face toward the religion, inclining to truth; the fitra of God upon which He originated mankind. There is no altering God's creation." The much-cited hadith completes it: "Every child is born upon the fitra; it is his parents who make him a Jew, a Christian or a Zoroastrian."
Read together with 7:172, the primordial covenant, in which God draws the descendants of Adam and asks "Am I not your Lord?", and they answer "Yes, we bear witness", the doctrine produces a theology in which faith is recovery rather than acquisition. Unbelief becomes a covering over of something already known, which suits the root meaning of kufr, to cover.
This is the standard point at which Islamic anthropology is contrasted with Christian doctrines of original sin. Islamic theology has no inherited guilt: Adam's lapse is his own, he repents and is forgiven (2:37), and every person is born sound and accountable only for what they do. Muslim theologians nevertheless differed over how much fitra delivers unaided, whether it yields actual knowledge of God prior to revelation, as Mu'tazili confidence in reason suggested, or only a receptivity that revelation is needed to actualise, the more common Ash'ari view. In jurisprudence the same word names something more modest: the sunan al-fitra, the acts of natural cleanliness such as trimming the nails and using the toothstick, listed in hadith as belonging to the way human beings were made to live.