Narrated 'Abu Salamah b. 'Abd al-Rahman and Sulaiman b. Yasar:

On the authority of some men of the Ansar : The Prophet ﷺ said to the Jews and started with them: Fifty of you should take the oaths. But they refused (to take the oaths). He then said to the Ansar: Prove your claim. They said: Do we take the oaths without seeing, Messenger of Allah? The Messenger of Allah ﷺ then imposed the blood-wit on the Jews because he (the slain) was found among them.

حَدَّثَنَا الْحَسَنُ بْنُ عَلِيٍّ، حَدَّثَنَا عَبْدُ الرَّزَّاقِ، أَخْبَرَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، وَسُلَيْمَانَ بْنِ يَسَارٍ، عَنْ رِجَالٍ، مِنَ الأَنْصَارِ أَنَّ النَّبِيَّ ﷺ قَالَ لِلْيَهُودِ وَبَدَأَ بِهِمْ " يَحْلِفُ مِنْكُمْ خَمْسُونَ رَجُلاً " . فَأَبَوْا فَقَالَ لِلأَنْصَارِ " اسْتَحِقُّوا " . قَالُوا نَحْلِفُ عَلَى الْغَيْبِ يَا رَسُولَ اللَّهِ فَجَعَلَهَا رَسُولُ اللَّهِ ﷺ دِيَةً عَلَى يَهُودَ لأَنَّهُ وُجِدَ بَيْنَ أَظْهُرِهِمْ .