Psalms 137:5 - Matthew Poole's English Annotations on the Holy Bible

If I forget thee; if I do not retain a deep and sorrowful sense of thy ruin and misery, or if I indulge myself in mirth and jollity, as if I had forgotten thee. Right hand; the chief instrument of playing upon musical instruments and of other actions. Forget her cunning, i.e. lose its skill of playing. In the Hebrew it is only forget, without expressing what, to intimate the extent and generality of this wish; Let it forget or be disenabled not only for playing, but for every action in which it was formerly used.