What does Acts 7:57 mean?

Stephen's accusers were angry that they couldn't refute his arguments that Jesus of Nazareth is the Messiah (Acts 6:8–15). They were furious when he defended himself, using Jewish history to show how hypocritical they were. But now, Stephen has claimed that he sees Jesus—the man who was crucified—standing at the right hand of God. This is something they cannot let go unchallenged.

One of the false accusations Stephen is charged with is that he "will change the customs that Moses delivered" to the Jews (Acts 6:14). Stephen's defense pointed out that the Jews were never good at following the Mosaic law, anyway. They much preferred worshiping foreign gods (Acts 7:39–43). Stephen's accusers are now stopping their ears. The phrase is also used in Zechariah 7:11. It literally means "made their ears too heavy to hear." In Zechariah 7, God is accusing the Jews of purposefully ignoring the parts of the Law aimed at protecting the vulnerable. But God also says, "They made their hearts diamond-hard lest they should hear the law and the words that the LORD of hosts had sent by his Spirit through the former prophets" (Zechariah 7:12). God responds to such resistance by allowing it to continue: "Make the heart of the people dull, and their ears heavy, and blind their eyes; lest they see with their eyes, and hear with their ears, and understand with their hearts, and turn and be healed" (Isaiah 6:10).

The last part of Stephen's defense is that the Jews would rather murder God's prophets than listen to them (Acts 7:52), a conviction also held by Jesus (Luke 11:47). Stephen's accusers are about to prove his point.