Psalms 27:7 - Albert Barnes' Notes on the Bible

Hear, O Lord, when I cry with my voice - This earnest prayer seems to have been prompted by a returning sense of danger. He had had assurance of the divine favor. He had found God ready to help him. He did not doubt but that He would aid him; yet all this did not prevent his calling upon Him for the aid which he needed, but rather stimulated him to do it. With all the deep-felt conviction of his heart that God was ready and willing to assist him, he still felt that he had no reason to hope for His aid unless he called upon Him. The phrase “when I cry with my voice” refers to the fact that he prayed audibly or aloud. It was not mental prayer, but that which found expression in the language of earnest entreaty.