Which Tzadik will rejoice?
Rashi: Daniel.
Radak: David says so about himself. He was Tzadik in his case; they pursued him without reason.
Malbim: Every Tzadik rejoices when justice is done.
Will the Tzadik rely on Hashem's shelter only in the future?
Radak #1: He will rely on it more when he sees His vengeance against enemies.
Radak #2: The prefix in "v'Chasah" is like Ki or Ka'asher, like the Vov is v'Sifsei Renanos (63:6). Now that they see vengeance against the enemies, they will rejoice that they relied on Him initially. They are not ashamed that they trusted; their hope was not lost.
How will the straight-hearted be praised?
Rashi: They will glorify themselves, for they are assured that Hashem helps them.
Radak: Just like I (David) am praised in Him.
Malbim: They are praised via serving Hashem and being saved via Him, and are praised through His name.
