Rabbi Elezar Ben Azaria was appointed the be the Nassi when he was only 18 years old.  Of course, many people were concerned that he was too young to be the leader of the Jewish People.

So, Hashem did a miracle.  Over night, he turned his hair and beard white.  This way, he would look like a wise, old man even if he was young. 

This is how he was LIKE 70...but not really 70.

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