If some people are (re)conciled on illegal basis, their reconciliation is rejected

Narrated Abu Huraira and Zaid bin Khalid Al-Juhani:

A bedouin came and said, "O Allah's Apostle! Judge between us according to Allah's Laws." His opponent got up and said, "He is right. Judge between us according to Allah's Laws." The bedouin said, "My son was a laborer working for this man, and he committed illegal sexual intercourse with his wife. The people told me that my son should be stoned to death;
so, in lieu of that, I paid a ransom of one hundred sheep and a slave girl to save my son. Then I asked the learned scholars who said, "Your son has to be lashed one-hundred lashes and has to be exiled for one year." The Prophet ﷺ said, "No doubt I will judge between you according to Allah's Laws. The slave-girl and the sheep are to go back to you, and your son will get a hundred lashes and one year exile." He then addressed somebody, "O Unais! go to the wife of this (man) and stone her to death" So, Unais went and stoned her to death.

حَدَّثَنَا آدَمُ، حَدَّثَنَا ابْنُ أَبِي ذِئْبٍ، حَدَّثَنَا الزُّهْرِيُّ، عَنْ عُبَيْدِ اللَّهِ بْنِ عَبْدِ اللَّهِ، عَنْ أَبِي هُرَيْرَةَ، وَزَيْدِ بْنِ خَالِدٍ الْجُهَنِيِّ، رضى الله عنهما قَالاَ جَاءَ أَعْرَابِيٌّ فَقَالَ يَا رَسُولَ اللَّهِ اقْضِ بَيْنَنَا بِكِتَابِ اللَّهِ. فَقَامَ خَصْمُهُ فَقَالَ صَدَقَ، اقْضِ بَيْنَنَا بِكِتَابِ اللَّهِ. فَقَالَ الأَعْرَابِيُّ إِنَّ ابْنِي كَانَ عَسِيفًا عَلَى هَذَا، فَزَنَى بِامْرَأَتِهِ، فَقَالُوا لِي عَلَى ابْنِكَ الرَّجْمُ. فَفَدَيْتُ ابْنِي مِنْهُ بِمِائَةٍ مِنَ الْغَنَمِ وَوَلِيدَةٍ، ثُمَّ سَأَلْتُ أَهْلَ الْعِلْمِ، فَقَالُوا إِنَّمَا عَلَى ابْنِكَ جَلْدُ مِائَةٍ وَتَغْرِيبُ عَامٍ. فَقَالَ النَّبِيُّ ﷺ " لأَقْضِيَنَّ بَيْنَكُمَا بِكِتَابِ اللَّهِ، أَمَّا الْوَلِيدَةُ وَالْغَنَمُ فَرَدٌّ عَلَيْكَ، وَعَلَى ابْنِكَ جَلْدُ مِائَةٍ وَتَغْرِيبُ عَامٍ، وَأَمَّا أَنْتَ يَا أُنَيْسُ ـ لِرَجُلٍ ـ فَاغْدُ عَلَى امْرَأَةِ هَذَا فَارْجُمْهَا ". فَغَدَا عَلَيْهَا أُنَيْسٌ فَرَجَمَهَا.