A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
psa 123:1An earnest and expecting prayer for divine aid in distress. (Psa 123:1-4)
(Compare Psa 121:1).
thou that dwellest--literally, "sittest as enthroned" (compare Psa 2:4; Psa 113:4-5).
psa 123:2Deference, 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 (Isa 9:13; Pe1 5:6; compare Gen 16:6); (5) to His rewarding hand.
psa 123:3contempt--was that of the heathen, and, perhaps, Samaritans (Neh 1:3; Neh 2:19).
psa 123:4of those that are at ease--self-complacently, disregarding God's law, and despising His people.