Here is a chunk from a video on EngVid (the whole piece starts at 0:21; the phrase in question is at 1:06):
You might have heard of this expression by Julius Caesar...
Similarly, modern times, Obama, in his inauguration speech said...
There's another example by Ben Franklin. Some people also say this is a Chinese proverb...
Now, what all three famous men here were doing was using what you're going to learn how to use by the end of this lesson, which is the "Magic of Three".
The three men have already been mentioned, but why is she not using the definite article when referring to them? She is even stressing this part, the word all.