The Torah says something strange when Balaam, the prophet hired by Balak of Moab to curse Israel, finally opened his mouth. And the Lord put a word in Balaam's mouth (Numbers 23:5). What is this "word"?
The Rabbis of the Midrash (Bamidbar Rabbah 20) give two answers. The first: an angel took a seat in Balaam's throat. When Balaam wanted to bless, the angel allowed the words through. When Balaam wanted to curse, the angel tickled his throat and stopped the curse cold. This is exactly the reading supported by a verse in the Psalms, where word is used of an angel: He sent His word and healed them (Psalms 107:20).
Rabbi Yochanan, however, preferred a harsher image. He taught that there was an iron nail lodged in Balaam's throat. When Balaam wished to bless, the nail let the sounds pass. When he wished to curse, the nail rasped against the walls of his throat and prevented speech. For word can also mean a physical object, as in every thing — or, in the Hebrew, every word — that may abide the fire (Numbers 31:23), which refers to metal vessels.
Either way, the teaching is the same. God did not silence Balaam by removing his voice. He left the voice intact and installed a gatekeeper. Blessings flowed. Curses died in the throat. Balaam could try all he liked. His tongue had been commandeered.
The 1901 anthology Hebraic Literature preserves this double reading, angel and nail, as a choice. The Rabbis are not deciding between them. They are offering the reader two pictures of the same truth: the enemies of Israel have always been free to plan, hire prophets, stage elaborate curses. What they have never been able to guarantee is that the curse will land.