Rashi on the Prophets and Writings
Psalms 23
The land...are the Lord’s The land of Israel. the world The other lands.
founded it upon seas Seven seas surrounded Eretz Yisroel and four rivers: the Jordan, Yarmuk, Karmion, and Pigah.
Who will ascend upon the Lord’s mount Although all the inhabitants of the world are His, not everyone deserves to come near to Him, except these: he who has clean hands, etc.
who has not taken My name in vain Who has not sworn with My name and My soul in vain. We find an expression of an oath used with the soul (נפש), as it is stated (in Amos 6:8): “The Lord God swore by Himself (בנפשו).”
This [generation,] whose deeds are such - this is the generation of those who seek him.
[You] gates, lift your heads In the days of Solomon his son, when he comes to bring the Ark into the Holy of Holies and the gates cling to each other, he [Solomon] recited twenty-four praises, but he was not answered until he said (II Chron. 6:42): “Do not turn back the face of Your anointed; remember the kind deeds of David, Your servant.”
everlasting portals Portals whose sanctity is everlasting.
You arrive at the cited line; the whole work is yours to read around it. The text is set from the cited public-domain edition.