Jamieson, Fausset and Brown on Psalms 123:2

2. Deference, submission, and trust, are all expressed by the figure. In the East, servants in attending on their masters are almost wholly directed by signs, which require the closest observance of the hands of the latter. The servants of God should look (1) to His directing hand, to appoint them their work; (2) to His supplying hand (Psa 104:28), to give them their portion in due season; (3) to His protecting hand, to right them when wronged; (4) to His correcting hand (Is 9:13; 1Pe 5:6; compare Ge 16:6); (5) to His rewarding hand.