Charles H. Spurgeon on Psalms 141:5

Let the righteous smite me, The word olh is seldom used in Scripture but to signify a severe stroke which shakes the subject smitten, and causeth it to tremble; see Pr 23:35 1Sa 14:16 Ps 74:6; and it is used for the stroke of the hammer on the anvil in fashioning of the iron (Isa 41:7). Wherefore the word dox following may be taken adverbially, as a lenitive of that severity which this word imports: "Let him smite me, but" leniter, benigne, misericorditer, "gently, kindly, friendly, mercifully": and so some translations read the words, "Let the righteous smite me friendly, or kindly." —John Owen.