A few weeks ago, I saw in a Siddur (I wish I could recall which one. It's not one of the "popular brands") a section at the end of Shacharit saying that there is a minhag to recite verses from the Torah that have exactly 3 words. I know that this is the minimum pasuk length. so I guess that makes the number 3 special, in some way.
What is the origin and reason of this minhag? Are there any specific groups of people who are diligent to follow this minhag?