What is the ruling on one whose hand accidentally touched a woman's anus?

If a man intentionally touches a strange woman, he has committed a forbidden act, and he must repent, seek forgiveness, feel remorse, and resolve not to return to it. This is based on the Prophet's (peace and blessings be upon him) saying: "For one of you to be stabbed in the head with an iron needle is better for him than that he should touch a woman who is not lawful for him," and his saying: "The hand commits zina, and its zina is touching." However, if the touching was unintentional, there is no sin upon him. If the one touched is his wife, there is no harm in it. In all cases, ablution (wudu') is not invalidated merely by touching unless something is discharged, such as madhy (pre-seminal fluid).