137:1 Sat - The usual posture of mourners.

137:2 Harps - Harps are here put for all instruments of musick.

137:3 A song - Such songs as you used to sing in the temple of Zion.

137:4 The Lord's - Those songs which were appointed by God to be sung only in his service.

137:6 If - If I do not value Jerusalem's prosperity more than all other delights.

137:7 The day - In the time of its destruction.

137:8 Happy - As being God's instrument to vindicate his honour, and execute his just judgments.