Acts 7:13

And at the second time Joseph was made known to his brethren; and Joseph’s kindred was made known unto Pharaoh.

Acts 7:13 is part of Stephen's review of Israel's history showing God's dealings with the children of Israel. That review traced the history from Abraham through Solomon. He gave it as his final testimony by the Holy Spirit before a hostile crowd as he faced death, so its significance belongs to that occasion, time, and place.

He used that history to defend himself and to show its spiritual meaning as made clear through Christ. In doing so he gave the same Old Testament testimony about Christ that Peter and Paul gave, showing that Moses and the prophets bear witness to Christ's mission and identity. The verse therefore belongs to the inspired proof from Moses and the prophets that Jesus is the Messiah, establishing His identity and His mission, suffering, death, resurrection, and ascension.

The verse shows that the voice of Christ spoke through the patriarchs and prophets from the days of Adam to Stephen's time. It shows that Christ is the key that unlocks the Old Testament and gives access to its rich treasures. It shows that all religious services and ceremonies are valueless if the Saviour revealed in them and represented by them is rejected.