John Calvin Commentary Psalms 122:7

"Peace be within thy walls, And prosperity within thy palaces." — Psalms 122:7 (ASV)

Peace be within thy bulwarks, and so forth. The two clauses express the same sentiment, and therefore, the meaning of the first is gathered from the second. The term peace signifies nothing other than prosperity. The noun שלוה, shalvah, in the second clause, sometimes signifies rest, but it is more frequently taken for abundance or prosperity. For this reason, I have translated the noun בחילך bechelech, within thy bulwark. I do not find fault with others who have translated it a ditch or outward wall; but the word bulwark agrees better with the word towers, which occurs at the end of the verse.

The substance is that David prays for the prosperity of the Church throughout its whole extent. Moreover, it should be noted that when he makes supplication for its external prosperity, this should not be understood as implying that he was unconcerned about its internal state or spiritual well-being; but using the imagery of walls, he wishes that on all sides the blessing of God may surround and fortify the holy city.