Remember not, O God, the sins of long ago; in tender mercy visit us, distressed and humbled low.
O Lord, our Saviour, help, and glorify your name; deliver us from all our sins and take away our shame
Then, safe within your fold, we will exalt your name; our thankful hearts with songs of joy your goodness will proclaim.
The poetry of this is quite nice. I read it aloud and the flow is great. It basically sums up two stanzas of detailed lists of sins of the nations, nineteen lines of poetry, down into one line, “Remember not, O God, the sins of long ago;” The full Psalm is a lot more raw than the paraphrase.
Southwell, the tune, is short and simple. In a minor key and very stepwise it is not hard to sing. The rhythm provides some interest with the dotted rhythm in the third phrase which breaks up the square feeling from the other three phrases. I would be inclined to ignore the half-note value for the first word of each verse and just have a quarter-note pick-up which then matches the other phrases.