When many disciples left, who said, "Lord, to whom would we go? You have the words of eternal life"?

Answer: Simon Peter

When Jesus asked the Twelve if they wanted to leave too, Simon Peter answered with these words.

“From that time on many of His disciples turned back and no longer walked with Him. So Jesus asked the Twelve, “Do you want to leave too?” Simon Peter replied, “Lord, to whom would we go? You have the words of eternal life. We believe and know that You are the Holy One of God.””— John 6:66-69 (BSB)