Kalamos (measuring rod) refers to a reedlike plant that grew in the Jordan Valley to a height of fifteen to twenty feet. It had a stalk that was hollow and lightweight, yet rigid enough to be used as a walking staff (cf. Eze. Eze. 29:6) or to be shaved down into a pen (3Jn. 3Jn. 1:13). The stalks, because they were long and lightweight, were ideal for use as measuring rods.1
4 A figure of speech: Zeugma. The verb measure is by this figure yoked to a second object which does not fit it as equally as the first, for worshippers would not be measured but taken account of.Jerome Smith, The New Treasury of Scripture Knowledge (Nashville, TN: Thomas Nelson Publishers, 1992), Rev. 11:1.
5 Monty S. Mills, Revelations: An Exegetical Study of the Revelation to John (Dallas, TX: 3E Ministries, 1987), Rev. 11:1.