They knew with certainty that I came from you, and they believed that you sent me.
I'm guessing that this is a translation issue, but I'm curious to hear expert opinion. Here Jesus is praying about "those you have given me" (verse 6 & 9), by which I presume He means His disciples or all Christians.
But a few verses earlier (John 16:31), Jesus says:
“You believe at last!”
From other texts, I gather that the disciples often lacked faith.
So why does Jesus here say they were certain about Him?