Thorns and thistles serve as a reoccurring metaphor for sin and the pain and suffering brought about by man's disobedience to God. Just as thorns and thistles can choke out surrounding plants, sin works in this manner in our lives. We must take care to weed out sin from our lives so it will not keep us from our calling. References to thorns in the Bible can also foreshadow God's great plan of redemption.