He was talking to His disciples. Thus, some among His disciples did not believe.
Amen.
Now that we have clarified that, can you discern from the context which of His disciples did not believe and which of His disciples did believe?
61 When Jesus knew in Himself that His disciples complained about this, He said to them, “Does this offend you? 62
What then if you should see the Son of Man ascend where He was before?63 It is the Spirit who gives life; the flesh profits nothing. The words that I speak to you are spirit, and
they are life. 64 But there are some of you who do not believe.” For Jesus knew from the beginning who they were who did not believe, and who would betray Him. 65 And He said, “Therefore I have said to you that no one can come to Me unless it has been granted to him by My Father.”
66
From that time many of His disciples went back and walked with Him no more. 67 Then Jesus said to the twelve, “Do you also want to go away?”
68 But Simon Peter answered Him, “Lord, to whom shall we go? You have the words of eternal life. 69 Also we have come to believe and know that You are the Christ, the Son of the living God.”
70 Jesus answered them, “Did I not choose you, the twelve, and one of you is a devil?” 71 He spoke of Judas Iscariot,
the son of Simon, for it was he who would betray Him, being one of the twelve. John 6:61-71
Here are the key verses, the one's left out of your quote, which leads me to believe that you may not understand which disciples didn't believe, and which disciples did believe that Jesus is the Christ, the Son of the living God.
Key Verse's -
From that time many of His disciples went back and walked with Him no more.
67 Then Jesus said to the twelve, “Do you also want to go away?”
68 But Simon Peter answered Him, “Lord, to whom shall we go? You have the words of eternal life. 69 Also we have come to believe and know that You are the Christ, the Son of the living God.
Those who walked away from Him, didn't believe anymore.
The twelve however did believe and demonstrated that they continued to believe by continuing to follow Him.
The twelve believed.
The other disciples no longer believed, in which their initial believing was in vain.
JLB