John Gill Commentary Jeremiah 26:15

"Only know ye for certain that, if ye put me to death, ye will bring innocent blood upon yourselves, and upon this city, and upon the inhabitants thereof; for of a truth Jehovah hath sent me unto you to speak all these words in your ears." — Jeremiah 26:15 (ASV)

But know you for certain, that if you put me to death Take this along with you, and then do as you will; that if you take away my life on this account, you may depend upon it; nothing is more certain than this:

you shall surely bring innocent blood upon yourselves, and upon this city, and upon the inhabitants thereof; that is, the guilt of innocent blood, which would cry for vengeance upon them that brought the accusation, and insisted upon his being brought in guilty; and upon those that sat in judgment, and condemned him; and upon all the inhabitants of the city of Jerusalem, who should agree to the putting him to death:

for of a truth the Lord has sent me unto you to speak all these words in your ears; and therefore I am no false prophet, and am clear of the charge brought against me; and have said nothing but what I had a mission and an order from the Lord for, of which you may assure yourselves; and therefore he will avenge my blood, should it be shed on that account; so that you will only increase your guilt, and add to that great load that lies upon you, and will be your ruin, unless you repent and reform.