Tafsiran Keluaran 5:8: Rashi, Rashbam, Or HaChaim & Rav Hirsch

ואת מתכנת הלבנים means the total number of bricks which each made per day when straw was being supplied to them — that total you shall impose upon them now also, in order that the service may be hard upon them.

מתכנת, the quota.כי נרפים הם, they are therefore able to make more of these bricks daily.

כי נרפים הם, "for they are lazy!" Who had ever suggested that the idea to sacrifice to their G'd originated in the relatively light burden of work that Pharaoh had imposed on the Israelites up until then? Perhaps what Pharaoh meant was that the Israelites felt that now that Moses had arrived their lot would become easier and that therefore they wanted to thank their G'd for that by offering up thanksgiving sacrifices so that He would cancel out the servitude altogether. Pharaoh countered this euphoria by making the workload heavier so that they would not even entertain any idea of their servitude being near an end, i.e. those lies that Moses had fed them.

כי נרפים signifies because they have loosened themselves from the work; therefore (this word in Rashi corresponds to על כן in the Hebrew text) their mind turns to idleness and they cry out, saying, נלכה וגו׳ LET US GO [AND SACRIFICE etc.].

מתכנת — This word, and ותכן (v. 18), and the words of the same root in (I Samuel 2:3) “And by Him actions are counted (נתכנו)” and in (2 Kings 12:12) “the money that was counted (המתכן)”, all have the meaning of counting.

נרפים — The work is loose (רפויה) in their hand and neglected by them so that they are loosened (הם נרפים) from it. In old French retrait.