Jamieson, Fausset and Brown on Matthew 23:13

13. But woe unto you, scribes and Pharisees, hypocrites! for ye shut up the kingdom of heaven against men--Here they are charged with shutting heaven against men: in Lu 11:52 they are charged with what was worse, taking away the key--"the key of knowledge"--which means, not the key to open knowledge, but knowledge as the only key to open heaven. A right knowledge of God's revealed word is eternal life, as our Lord says (Joh 17:3; 5:39); but this they took away from the people, substituting for it their wretched traditions.