Why does it say "Asher"?
Radak: This is great Tzedakah (to lift us after we sank in the depths)!
Malbim: This shows that Your salvation is miraculous - great, evil afflictions are the cause of reviving us. Based on nature, afflictions kill! Also, raising me from the depths, and the lowliness is a cause of grandeur [was against nature].
Why is it written Hirisanu, and we pronounce it Hirisani?
Radak: The Kesiv is plural, for all Bnei Galus; the pronunciation is singular, like the Klal. Similarly it is written Techayenu, and we pronounce it Techayeni. Even though David said this Mizmor about himself, via Ru'ach ha'Kodesh he included matters of Bnei Galus. Just like he was exiled and in great affliction, and afterwards came to serenity and returned to Yerushalayim, from which he was exiled due to Avshalom, so Yisrael, who are exiled among the nations, will leave affliction to serenity, and return to Yerushalayim, Ir ha'Kodesh. From here until the end of the Mizmor discusses Bnei Galus.
Radak: The Meforshim say that the entire Mizmor is about David. If so, the plural refers to him and those with him.
Why does it say "Techayenu"?
Radak: We saw such great, terrible evils in Galus, to the point that all Goyim said that we will be finished off in Galus. We were like Mesim, and You will revive us!
Why does it say "umi'Tehomos ha'Aretz"?
Radak: It is as if we had sunk in the depths of the land, and You will lift us from there.
