Why should he look to Shamayim?
Rashi: See that He is high, and you are low. He has no benefit from your virtue or evil. Why do you glorify yourself about your virtue?
What is "Shur"?
Ibn Ezra: See. This is like "Ashurenu."
Why did he add "Sechakim Gavhu Mimeka"?
Malbim: Sechakim are even higher than Shamayim. This shows that Shamayim, which is so far away, cannot force your deeds 1 . Also, your good or bad deeds cannot affect Shamayim, and all the more so they cannot affect Hashem, who is much higher and distant!
Indeed, physical forces are weak from a far distance away. However, why can't supernatural forces work from far away? Hashem forced Pharaoh and Bil'am! (PF)
