This is my best 'explanation' for Psalm 123 at this time. Praying the psalms daily, I begin to wonder if I am really getting the full sense of the psalm, especially since they are translated. I found a KJV translation I like here for Psalm 123, and Hebrew translations for each word are on the same website.

Psalm 123
[A Song of Ascent]

Unto thee lift I up mine eyes,
O thou that dwellest in the heavens.

As the eyes of servants unto the hand of their master,
As the eyes of a maiden unto the hand of her mistress,
So our eyes unto the Lord, our God,
Until that he have mercy upon us.

Have mercy upon us, O Lord, have mercy upon us:
For we are exceedingly filled with contempt.

Our soul is exceedingly filled with the scorning of those that are at ease,
with the contempt of the proud.

[A Song of Ascent]

We are going to sing a song about ascending a ladder and journeying to a higher place. The Hebrew word ascent translated can also mean step, degree, a thought arising. It seems to focus our attention not to the top of the ladder, the end, but rather to each rung along the way, each step. So in this song our eyes are turned upward, but only just enough to see the next rung. As we sing, we begin to move up the ladder.

Unto thee lift I up mine eyes
O thou that dwellest in the heavens

We begin to sing. "We are lifting our eyes to thee, to thou who sits in heaven." Thee? Thou? The song does not say who it is yet. But already we are lifting and ascending and moving forward. The first word of this psalm in Hebrew is unto. It is a word that signifies motion toward, near, on and it seems to be the defining word for this psalm. We are holding up our vision toward the one we cannot yet name who is beyond our vision and enthroned in the heavens.

As the eyes of servants unto the hand of their master
As the eyes of a maiden unto the hand of her mistress
So our eyes unto the Lord, our God
Until that he have mercy upon us

There are many ways to imagine how a servant or a maid might look on the hands of a master. Is it during a feast, when he waits for a sign from his master's hand to fill his cup? Or at night when the tired servant returns from working in the field and stands dully by his master's side without thinking about anything? Or when the master has his hand raised to punish the servant? Or when invaders come and the master gives orders for the protection of the household? Or when the mistress is preparing for the feast and the maid sits by, watching as she combs her hair? Day in and day out the servant and maid keep their eyes on the hand of their master. It becomes not only a habit but something to live by.

The song does not end here. It sings: So our eyes unto the Lord, our God. The earthly images lead us to make a heavenly comparison. We are that servant and that maiden. God is our master. In the same way, our eyes reach toward the Lord, our God, so that he will stoop down to our level in kindness. "Lord, our God" can be translated as "Yahweh, our Elohim" which means the "eternal Master" who is "master over all masters". The Hebrew word for mercy means "to stoop in kindness toward an inferior," which is how a good master knows his servant.

Have mercy upon us, O Lord, have mercy upon us:
For we are exceedingly filled with contempt

Our soul is exceedingly filled with the scorning of those that are at ease,
with the contempt of the proud.

God is not like earthly masters. After all, who are we calling him to save us from in these lines but earthly masters? Earthly masters have the power and luxury to be careless, lazy, and arrogant, to shame and scorn us. It is not that God is like the masters. Rather, it is they who are meant to be like him. We have not yet seen a good master until we have lifted our eyes to the hand of God.

In Conclusion
Psalm 123 lifts our eyes with difficulty toward our true definition and God's. We begin by singing of what we have experienced or can easily imagine, and then we say that this is how we are with the Lord. A deeper knowledge of who we are is revealed. How do we take the leap from master and mistress to God? How can we know that they are images of him? It makes me think of the disciples on the road to Emmaus who, after they have discovered they were in the presence of Christ, exclaim: "Were not our hearts burning within us?" It is the same with these beautiful images of servants and masters. The images speak something to our hearts that we do not understand until we are told.