John Calvin Commentary Psalms 27:3

"Though a host should encamp against me, My heart shall not fear: Though war should rise against me, Even then will I be confident." — Psalms 27:3 (ASV)

Though armies should encamp. He infers from his past experience, as I have already mentioned, that whatever adversity may happen to him, he ought to continue to hope and to have no doubts about the divine protection, which had been so effectively granted to him in his previous need. He had asserted this, indeed, in the first verse, but now, with further proof of it, he repeats it.

Under the terms, camps and armies, he includes whatever is most formidable in the world. It is as if he had said, "Although all people should conspire for my destruction, I will disregard their violence, because the power of God, which I know is on my side, is far greater than theirs."

But when he declares, My heart shall not fear, this does not imply that he would be entirely devoid of fear—for that would have been more like insensibility than virtue. Instead, to prevent his heart from fainting under the terrors he had to encounter, he opposed them with the shield of faith.

Some transfer the phrase translated in this to the following verse, meaning that he was confident that he would dwell in God’s house. However, I am of the opinion that it belongs more to the preceding doctrine.

For it is then that faith produces its fruit in due season: when we remain firm and fearless in the midst of dangers. David, therefore, suggests that when the trial comes, his faith will prove invincible because it relies on the power of God.