Charles H. Spurgeon on Psalms 137:5

Let my right hand forget. Something must be supplied from the context...the playing on the stringed instrument, Ps 137:2, whether the right hand should be applied to the purpose or not, was the point in question. Then, the punishment also perfectly accords with the misdeed, as in Job 31:22: If I, misapplying my right hand to the playing of joyful strains on my instrument, forget thee, Jerusalem, let my right hand, as a punishment, forget the noble art; and then also Ps 137:6 fits admirably to what goes before: May my misemployed hand lose its capacity to play, and my tongue, misemployed in singing cheerful songs, its capacity to sing. —E. W. Hengstenberg.