Blessed are those who didn't see yet believe

 Today's Catholic gospel reading 

John 15:26-16:4a

At that time: Jesus said to his disciples, “When the Counsellor comes, whom I shall send to you from the Father, even the Spirit of truth, who proceeds from the Father, he will bear witness to me; and you also are witnesses, because you have been with me from the beginning. I have said all this to you to keep you from falling away. They will put you out of the synagogues; indeed, the hour is coming when whoever kills you will think he is offering service to God. And they will do this because they have not known the Father, nor me. But I have said these things to you, that when their hour comes you may remember that I told you of them.”

Many will hear the spirit of truth,the counsellor of the church  yet will still fall away in disbelieve like Thomas until they see. 

Which Jesus warns his disciples that blessed are those who didn't see yet believe.