John 5: 41-47, The Pharisees Are Accused by Moses

The Pharisees, who have questioned the right of Jesus to heal on the Sabbath, are accused of ignoring the Scriptures (the Old Testament writings.)

John 5: 39-40, Vain study of the Scriptures

You study the Scriptures diligently because you think that in them you have eternal life. These are the very Scriptures that testify about me, 
40 yet you refuse to come to me to have life.

Jesus accuses the Pharisees of diligently studying the Torah and the Prophets yet ignoring the One they point to, the Messiah who brings life and salvation.  Those scriptures, says Jesus, testify about Him!

John 5: 41-47, Pharisees accused by Moses

“I do not accept glory from human beings, 
42 but I know you. I know that you do not have the love of God in your hearts. 
43 I have come in my Father’s name, and you do not accept me; but if someone else comes in his own name, you will accept him. 
44 How can you believe since you accept glory from one another but do not seek the glory that comes from the only God?

45 “But do not think I will accuse you before the Father. Your accuser is Moses, on whom your hopes are set. 
46 If you believed Moses, you would believe me, for he wrote about me. 
47 But since you do not believe what he wrote, how are you going to believe what I say?”

The Pharisees, are accused of not loving God, despite their appearances.  They like to appear religious but that is an act.  In verse 43, Jesus implies that they would easily accept the testimony of a convenient liar who (verse 44) gives them glory, while ignoring the glory of God.

Although it is Jesus scolding them now, their accuser is their hero, Moses.  Again, Jesus emphasizes that the scriptures -- here the Torah of Moses -- point to him, Jesus.  That they have essentially ignored Moses for their own ends means that they will not believe Jesus.

Once again, the writer of the gospel put in front of his readers the issue of belief in the words of the Messiah.  Here those words are identified as previously spoken by Moses and the Scriptures.