and they shall answer and say, Our hands have not shed this blood, neither have our eyes seen it.
Deuteronomy 21:7 KJV COMMENTARY MEANING https://bible.com/bible/1/deu.21.7.KJV
This was very symbolic, innocent blood has been shed and now the elders kill an innocent heifer and wash their hands ever the bloody animal saying that they have not shed innocent blood.
The animal here seem to represent the dead whose blood had been shed just like this heifer.
The rituals of Israel was full of replacements substitution and atonements https://bible.com/bible/1/deu.21.7.KJV1