Adam Clarke on Psalms 129:8

Neither do they which go by say - There is a reference here to the salutations which were given and returned by the reapers in the time of the harvest. We find that it was customary, when the master came to them into the field, to say unto the reapers, The Lord be with you! and for them to answer, The Lord bless thee! Rut 2:4. Let their land become desolate, so that no harvest shall ever more appear in it. No interchange of benedictions between owners and reapers. This has literally taken place: Babylon is utterly destroyed; no harvests grow near the place where it stood.