as Sarah obeyed Abraham, calling him lord, whose children you now are, if you do well, and are not put in fear by any terror.

 In this passage we can see how Peter was soaked in the Old Testament; there are two Old Testament foundations for it. It is not so much that he actually quotes them, as that he could not have written the passage at all unless the Old Testament had been in his mind. The very first sentence is a reminiscence of Isaiah 50:9: "Behold, the Lord God helps me; who will declare me guilty?" Again, when Peter is talking about the banishing of fear, he is thinking of Isaiah 8:13, "But the Lord of hosts, him you shall regard as holy; let him be your fear, and let him be your dread." 