That's why Jesus also criticized the scribes: [Matthew 23:15] Woe to you, scribes and Pharisees, hypocrites! For you travel across sea and land to make a single proselyte, and when he becomes a proselyte, you make him twice as much a child of hell as yourselves.

And he also promised us the holy spirit:
[John 14:26] But the Helper, the Holy Spirit, whom the Father will send in my name, he will teach you all things and bring to your remembrance all that I have said to you.

Because faith needs the Spirit of truth to stay vivid.