Is a man held accountable if his penis accidentally exits his wife's vagina and enters her anus for less than a second during intercourse?

Engaging in anal sex with one's wife is a major sin. The Prophet, peace and blessings be upon him, cursed the one who does it, saying: "Accursed is he who has intercourse with a woman in her anus," and "Whoever has intercourse with a menstruating woman, or with a woman in her anus, or consults a soothsayer, has disbelieved in what was revealed to Muhammad." However, if someone commits this act by mistake and without intention, there is no sin upon them, as Allah Almighty says: "Our Lord, do not impose blame upon us if we have forgotten or erred" (Quran 2:286), and "And there is no blame upon you for that in which you have erred, but [only for] what your hearts have intended" (Quran 33:5). And the Prophet, peace and blessings be upon him, said: "Indeed, Allah has pardoned for my Ummah their mistakes, their forgetfulness, and what they are forced to do."