Verse 10. “And I said This is my infirmity; but I will remember the years of the right hand of the most High.” It is the “infirmity” of the believer to be always thinking of himself, and drawing false inferences from what he sees and feels in himself, with regards as to how he is held and estimated on the part of God. It is his strength, on the other hand, to remember “the right hand of the most High.” To meditate upon the changeless truth and mercy of that God who has committed himself in holiness to the believing sinners sure salvation, by causing the Son of His love to suffer in our stead the dread reality of penal death.
Arthur Pridham
Verse 10. “... the years of the right hand of the most High.” Not the moments, nor the hours, nor the days, of a few short afflictions, that His left hand hath dealt to me; but “the years of the right hand;” - those long, large, and boundless mercies wherewith He hath comforted me.
Thomas Adams
Verse 11. “I will remember the works of the Lord; surely I will remember thy wonders of old.” Faith has a good memory, and can tell the Christian many stories of ancient mercies; and when the believer's present meal falls short, faith can entertain the soul with a cold dish, and not complain that God keeps a bad house. Thus David recovered himself when he was even tumbling down the hill of temptation. “This is my infirmity … but I will remember the wonders of old.” Therefore, Christian, when thou art in the depths of affliction and Satan tempts thee to cast aspersions at God – as if God were forgetful of thee – stop his mouth with this: “No, Satan, God has not forgotten to do for me, but I have forgotten what He has already done for me, or else I would not question his fatherly care over me at this present time.” Go, Christian, look over thine own lessons; praise God for past mercies, and it will not be long before thou hast a new song put into thy mouth for a present mercy.
William Gurnall
Verse 13. “Thy way, O God, is in the sanctuary ...” Only in God's presence is God's providence understandable. As David has earlier been perplexed at the prosperity of the wicked, “until,” as he says, “I went into the sanctuary of God, then understood I their end.” The heart is easily led astray from God's ways by what the eye imagines it sees; only in God's presence through His truth is it rightly focussed to discern the paths of righteousness. Yet, we must remember that God is God, and often His providences and purposes lie hidden for manys a year. Martin Luther tells of a time when he sought and sought the Lord's directive for a certain course, and only ever received the answer - “I am not to be traced.” “Well, then,” said Luther, “If He is not to be traced, He may yet be trusted.” John Flavel hit the nail aright when he remarked, “Some of God's providences are like Hebrew letters, they must be read backwards.”
Verse 20. “Thou leddest thy people like a flock by the hand of Moses and Aaron.” He does not say that Moses and Aaron led the people of Israel, but Thou leddest the people – Thy people - by the hand of Moses and Aaron. Great was the power of these two men; nevertheless, neither of them was the true shepherd of the sheep, but each was a servant to the one and only True Shepherd, to whom the sheep exclusively belonged. Nor yet, was either the leader of the sheep, but the shepherd Himself was present and led his own flock, to which these two acted as servants.
There are, therefore, three things to be learned from this passage. First, the sheep do not belong to the servants, but to the true shepherd. Secondly, the true shepherd is the leader of His own sheep. Thirdly, the office of Moses and Aaron was to attend to this duty, that the Lord's sheep should be properly led and pastured. So Christ Himself leads his sheep, His own sheep, yet for this work He employs the ministry of His servants.
Musculus
Verse 20. “Thou leddest thy people like a flock ...” What a transition from tempest to peace, from wrath to love. Quietly as a flock Israel was guided on by human agency which veiled the excessive glory of the Divine presence. The smiter of Egypt was the Shepherd of Israel. He drove His foes before Him, yet went before His people. Therefore, with devout joy and full of consolation, we close this psalm. It is the song of one who at the beginning, had forgotten how to speak, and yet learned to sing far more sweetly than all his fellows.
Charles Haddon Spurgeon