Arabic is based on a tri-lateral root system. What that means is that majority of words go back to 3 root letters which give it its base meaning. Let’s look at an example:
The three letter root د- ر- س means to study. From there we get a myriad of words such as:
- دَرْسٌ – lesson
- مَدْرَسَة – school
- دِرَاسَة – studying
- مُدَرِّس – instructor
While they mean different things, they all have a relation to “study.” Knowing the three letter root helps because even if you don’t know the words you can make an educated guess based on the three letter root. Also, a quick rule of thumb: م and ت are usually not root letters.
So now let’s look at the word مُصْطَفَى. There seems to be a lot of words, so let’s break it down.
As we said, م is usually not a root letter. Now we are letter with ص، ط، ف، ى. This means one of these letters is not part of the root letter. So what is happening?
The word مُصْطَفَى comes from the pattern of اِفْتَعَلَ where the root letters are فعل.
(These are generally used as a template which can be replaced. For example, in the word اختلف, the root letters are خلف which followed the same pattern as افتعل)
The pattern of افتعل is tricky because it has some irregularities, especially with the ت. The reason is because ت is a light letter, and it becomes difficult to pronounce the ت if a heavy letter precedes it. An example of this ضرب. If we apply it on the pattern of افتعل you end up with اضترب. But pronouncing the ض, which is a heavy letter and then quickly switching to the ت becomes too difficult. The solution to this is to change the ت to its heavier version, ط so that pronouncing it is easier. So now that we understand this, let us go back to our original question.
What are the root letters for the word مُصْطَفَى?
مُصْطَفَى does fall under the pattern of افتعل, however we see no ت . That is because the letter before it, ص is a heavy letter, and thus forced the ت to become a ط. Thus, the only letters left are ص، ف، ى which means to be pure. مُصْطَفَى means to be chosen, but not just any type of choosing, a choosing based on purity. Thus, that is why the Prophet is called مُصْطَفَى.