Radak

Thou hast rebuked the nations (גוִֹיִם גערת): – (The expression for) rebuke when used without the preposition beth has the meaning of destruction, as: “Rebuke the wild beast of the reed” (Ps. 68:31); and as, “Behold, I will rebuke the seed for your sake” (Mal. 2:3); and so Thou hast rebuked (the) nations here. And he says, Thou hast rebuked the nations – these being the Philistines. Thou hast destroyed the wicked (man): – viz. Goliath the Philistine. Thou hast blotted out their name: – speaking of the dead in the war, as it is said (1 Sam. 17:52), “And the despatched of the Philistines fell.” for ever and aye (וָעֶד): – This word (וָעֶד) signifies a longer duration of time than עולם (for ever). Unless immediately before the end of a verse, it is pointed with pathah; (and so also) when without (the accent) ‘athnah, as (in the passage): “And do not for ever (לָעַד) remember iniquity” (Is. 64:8); and (even) with ’athnah, as (in the passage): “Knowest thou this from old time (מִנִּי־עַד)” (Job 20:4); but at the end of a verse (in the form) לעולם ועד, with seghol.