The second detail in Peter’s response is a call for courage. He tells his readers that they should not be afraid of their opponents or troubled by what they might do.
Is Peter’s mind going back to the upper room in Jerusalem when Jesus instructed his disciples, as they were about to go into a period of trouble even if they did not know it then, that they should not let their hearts be troubled or afraid (John 14:27)? Peter could recall the uselessness of natural courage at that time, so he cannot be advising his readers to trust in their own resources. Instead he is urging them to look for courage from God.
Or is Peter referring to Isaiah 8:11 and 13, in which the prophet uses similar ideas to the apostle? In verse 13, the prophet says, ‘But the Lord of hosts, him you shall regard as holy. Let him be your fear, and let him be your dread.’ It does have similar ideas to Peter about sanctifying the Lord. From that verse it is clear that the only way to avoid the fear of man is to fear God in a reverential way. Such a fear caused Moses to leave Egypt, caused Daniel and his friends to disobey the Emperor of Babylon, and led Peter and John to ignore the threats of the authorities. The list could be extended down the centuries.
Peter would agree with Paul’s exhortation to the Ephesians that they should be strong in the Lord and in the power of his might. There is such a thing as spiritual courage, which can make even the timidest believer turn into a Daniel. In spiritual courage, there is dependence on Christ and determination to serve him fully wherever he places us, whatever the difficulties or problems. There is also an assessment of the strength of the enemy in comparison to the strength of Christ – one sure way to lose courage is by over-estimating the power of one’s opponents. Further, we can obtain courage by acknowledging the providence of God in allowing them. These aspects of courage must always be fresh in our experience. Yesterday’s resolve is of no use today.