Acts 7:51-53 – What does Stephen allude to when he said “as your fathers -also ye” (v 51b), killing prophet (s) or not keeping the law?

Acts 7:51-53 You stiff-necked people, uncircumcised in heart and ears, you always resist the Holy Spirit. As your fathers did, so do you. Which of the prophets did your fathers not persecute? And they killed those who announced beforehand…