And they shall answer and say, Our hands have not shed this blood, neither have our eyes seen it.

Wesley's Notes

21:7 They shall answer - To the priests who shall examine them. This blood - This about which the present enquiry is made: or this which is here present: for it is thought the corps of the slain man was brought into the same place where the heifer was slain. Nor have we seen or understood how or by whom this was done.

Matthew Henry's Concise Commentary

21:1-9 If a murderer could not be found out, great solemnity is provided for putting away the guilt from the land, as an expression of dread and detesting of that sin. The providence of God has often wonderfully brought to light these hidden works of darkness, and the sin of the guilty has often strangely found them out. The dread of murder should be deeply impressed upon every heart, and all should join in detecting and punishing those who are guilty. The elders were to profess that they had not been any way aiding or abetting the sin. The priests were to pray to God for the country and nation, that God would be merciful. We must empty that measure by our prayers, which others are filling by their sins. All would be taught by this solemnity, to use the utmost care and diligence to prevent, discover, and punish murder. We may all learn from hence to take heed of partaking in other men's sins. And we have fellowship with the unfruitful works of darkness, if we do not reprove them.