In the beginning of the parsha, when it starts to discuss the red cow, it says, “וידבר ה’ אל משה ואל אהרן לאמר – And Hashem told Moshe and Aharon to say.” But after that, it says the word לאמר – to say – again: “.אשר צוה ה’ לאמר” The Kli Yakar wonders why it had to say it again.
He answers with what Rashi says: That the nations of the world make fun of us because we don’t know why we use the ashes of the parah adumah – red cow – to purify ourselves. Rashi says that’s why it calls it a chukah, meaning it’s a decree of the King, and we are obligated to do it even if we don’t know the reason. The Kli Yakar says based on this Rashi that this is why it uses the word leimor, to say, again. Hashem commands us to respond to them that it’s a chukah – a decree.
[Heard from Ariel Weinreich]