Acts 6:14

for we have heard him say, that this Jesus of Nazareth shall destroy this place, and shall change the customs which Moses delivered unto us.

'WE HAVE HEARD HIM SAY'-The fact that the witnesses are called false witnesses, infers that they distorted or misrepresented Stephen's preaching. Or, they didn't reveal the rest of the sermon that would put the following words into. more favorable light.

'THIS JESUS OF NAZARETH SHALL DESTROY THIS PLACE'-i.e. this Temple. And Jesus had taught such (Matthew 24:3; Luke 19:41). What is left out, is that such would happen because of their rebellion to God (Matthew 23:37).

'SHALL CHANGE THE CUSTOMS WHICH MOSES DELIVERED UNTO US'-'"Customs" are the ceremonial rites and observances--sacrifices, festivals, clean and unclean meats, etc....including the whole complex system of the mosaic law--it's rituals, symbolism, regulations for daily living, circumcision, Sabbath-keeping, etc..See Acts 15:1 ff; Acts 21:21.' (Reese p. 263)

Points to Note:

The concept was true, the New Covenant did "change the customs" (Colossians 2:16; Galatians 5:1; The Book of Hebrews).

But the impression given in the accusation, especially when occupied with the charge of blasphemy, is that the false witnesses were inferring that Stephen had been saying that such customs were meaningless or had never been important. Stott notes, 'What Jesus taught, then, was that the temple and the law would be superseded, meaning not that they had never been divine gifts in the first place, but that they would find their God-intended fulfillment in him...Moreover, to affirm that both temple and law pointed forward to him and are now fulfilled in him is to magnify their importance, not to denigrate it...The False witnesses accused him of saying that Jesus of Nazareth would destroy the temple and change the law. That is, they portrayed the work of Christ in negative, destructive terms. But what Stephen was really doing was preaching Christ, positively and constructively, as the One in whom all that the Old Testament foretold and foreshadowed is fulfilled, including the temple and the law.' (p. 129)

Notice how Jesus elevated the Law of Moses at the same time predicting it's removal (Matthew 5:17). Paul does the same thing in Galatians 3:21.