Rashi: He has mercy on the Tzadik. He loves those whose insides are straight.

Radak: He loves a man of Tzedakos.

Malbim: This explains how Hashem tests the Tzadik. If Hashgachah was revealed, and a Tzadik was rewarded immediately, he would intend to do Tzedek for the reward. However, Hashem ha'Tzadik loves Tzedakos on condition that "Yashar Yechezu Paneimo" - they look straight opposite His face. I.e. the motivation was only l'Shem Hashem, but not if it was for reward. Then, he does not look straight to Hashem, rather, crookedly. His eyes look towards the reward. Hashem does not love such Tzedakos. Therefore, Hashem hides the reward for Avodah, and he finds difficulties and afflictions, and this tests that he does Tzedakos only l'Shem Hashem, and face straight at Him.

Rashi: This refers to the beginning of the verse - Hashem loves Tzedakos.

Radak #1: A straight man, his face is seen. This is like "u'Fanisi Aleichem" (Vayikra 26:9). Paneimo is like Paaav. Similarly, "Ki Yiskon Aleimo Maskil" (Iyov 22:2) is like Alav.

Radak #2: This is [Hashem's countenance,] like "Ani b'Tzedek Echezeh Fanecha" (17:15).

Radak #3: Hashem, who is straight, sees the face of Tzadikim. Paneimo is like Peneihem (their face. [The suffix] Mem Vov is plural.

Radak, based on Shocher Tov: It should have said Yesharim Yechezu Fanav, or Yashar Yechezeh Fanav. Why does it say "Yashar Yechezu Paneimo"? The straight One of the world, the faces of the straight will see Him ¹ .

Malbim: Refer to 11:7:1:3.