Draw out also the spear, and stop the way against them that persecute me: say unto my soul, I am thy salvation.
Draw out also the spear - namely, from thy armoury.
And stop (the way) - interpose thyself, between me and my persecutors; literally, 'set a barrier' against them. David, as a warrior, uses martial images.
My soul (or life), I am thy salvation - not merely my Saviour, but my salvation, embodying in thyself all salvation. Contrast Acts 16:30, "What must I do to be saved?" Make me, by actual deliverance of my endangered soul, to feet that thou hast spoken the word which works its own effect, "I am thy salvation." The realized "salvation," not an audible saying, is what he prays for from God.