Sahih Ibn Khuzaymah

And the Prophet (ﷺ) informed him that Allah, the Exalted, had forgiven him due to his ablution and performance of prayer; it was a sin less than adultery which necessitates the prescribed punishment.

Because every act from which Allah Almighty has strictly forbidden is subject to the application of a hadd (legal limit); hadd is not only for those sins which make whipping, stoning, or cutting of hands and feet obligatory. Allah Almighty, mentioning the divorced woman, said: « لَا تُخْرِجُوهُنَّ مِن بُيُوتِهِنَّ .... فَقَدْ ظَلَمَ نَفْسَهُ » [ سورة الطلاق ] "Do not expel them from their houses, nor should they leave on their own, unless they commit a clear immorality. These are the limits set by Allah. Whoever transgresses the limits of Allah has certainly wronged himself." And the statement of Allah Almighty is: « تِلْكَ حُدُودُ اللَّهِ فَلَا تَعْتَدُوهَا » [ سورة البقرة ] "These are the limits set by Allah, so do not transgress them." Therefore, the act from which Allah Almighty has rebuked is subject to the application of a hadd, because Allah Almighty has commanded to stay within those limits, so one should not transgress or go beyond them.