Hummel is known for his essay, "Tyranny of the Urgent", published in 1967 as a booklet by InterVarsity Press, which became popular as guide to time management and personal productivity in both ministry and business circles, and has since undergone periodic updates and revisions. In 1997 he published "Freedom from Tyranny of the Urgent", an expansion upon his original work.
During his life Hummel authored fifteen books and Bible studies.