Ruling on blood coming from the nose during prayer

Question:
May Allah reward you. He says: I was praying the 'Asr prayer when blood came from my nose without any intention on my part, and it was about five or four drops. What is the ruling?

Answer:
Blood coming out does not invalidate the wudu' if it is a small amount, whether from the nose or elsewhere. So the prayer is valid and the wudu' is not invalidated, and there is no blame in that. When he is finished, he should clean himself afterwards.
As for if it is a large amount, the safest course is to perform wudu'; because some scholars say that a large amount of blood invalidates the wudu'. Some weak hadiths and some athar have been reported regarding this.
So if he performs wudu' and repeats his prayer and repeats his wudu', that is more preferable and safer. However, there is no clear text stating that a large amount of blood invalidates the wudu'. It is a difference of opinion among scholars due to athar reported on this matter that contain weakness, and athar from some of the Companions. So if he performs wudu' as a precaution, that is good.