Describe symbolism in God's Trombones: Seven Negro Sermons in Verse by James Weldon Johnson

In the poem, Listen, Lord—A Prayer, the people are referred to as empty pitchers waiting to be filled by God. In the ninth line of the third stanza of this poem the speaker asks the Lord to make the preacher's words, "sledge hammers of truth." It is also requested that the preacher's imagination be cleaned with turpentine and that he be allowed to see the "paper walls of time" through the "telescope of eternity." Notice that all of these symbols the speaker uses are things that the congregation would encounter in their everyday life and be very familiar with.