What measure of Shamayim is discussed?
Rashi: Its height [above the ground].
What is the connection of measuring Shamayim va'Aretz to not despising Yisrael?
Rashi: Just like one cannot measure Shamayim or investigate the foundations of the land below, so Yisrael will not be despised, in spite of the sins that they will do.
Radak (35): After comparing the endurance of Yisrael in the true way to the laws of Shamayim, He compares His love for them to measuring Shamayim above and investigating the foundations of the land 1 below. Just like the latter is impossible for man, so Hashem cannot separate from Yisrael and despise them.
Malbim: Just like Shamayim will not change its deeds, I will not change to despise them via their earlier sins, for My love for them has no bound, just like there is no measure for Shamayim. One cannot understand via investigation why I love them, just like one cannot investigate the foundation of the land below. Even though one can measure its quantity, one cannot know their essence. Anything without investigation or reason is like a Segulah, which cannot be Batel. Something with a reason, when the reason is Batel, it is Batel. Something based on Segulah is different.
Radak: Measuring applies to Shamayim, for it is spread. It mentions the foundations of the land which is below, like the foundation of a building. Also another verse discusses these - "Af Yadi Yasdah Eretz vi'Ymini Tipchah Shamayim" (Yeshayah 48:13).
Why does it say "Al Kol Asher Asu"?
Rashi: [Yisrael will not be despised] in spite of the sins that they will do. Radak - this is because He will pardon them, like it says above (33).
