Many have the practice to recite, in the prayer following Shemoneh Esrei, a verse that starts and ends with the same letter as their name, or that contains their name. This is the verse for the name “Yitzchak.” This verse refers back to verse 10. There, the Metzudas David explains that “the shadow of death” means the threat of death and “darkness” means the impending darkness of the grave. Taking us “out of darkness” is therefore a metaphor meaning to save our lives.