Hadith 6906
Then Muhammad bin Maslama testified that he had witnessed the Prophet giving such a verdict.
Hadith 6908
قَالَ : ائْتِ مَنْ يَشْهَدُ مَعَكَ عَلَى هَذَا ، فَقَالَ
مُحَمَّدُ بْنُ مَسْلَمَةَ : أَنَا أَشْهَدُ عَلَى النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ بِمِثْلِ هَذَا " .
Umar said, "Present a witness to testify your statement." Muhammad bin Maslama said, "I testify that the Prophet gave such a judgment."
Hadith 7318
So I went out, and found Muhammad bin Maslama. I brought him, and he bore witness with me that he had heard the Prophet saying, "Its Diya (blood money) is either a male slave or a female slave."