Thou hast a mighty arm - Margin, as in Hebrew," an arm with might." That is, Thou hast great power - the arm being the instrument by which we accomplish our purposes.
Strong is thy hand - The hand, too, is an instrument by which we execute our plans. Hence, God is so often represented a having delivered his people with a strong hand.
And high is thy right hand - It is by the right hand particularly that we carry out our purposes. We lift it high when we are about to strike with force. All this is expressive of the divine omnipotence.

Thou hast a mighty arm,.... Christ is the arm of the Lord, and a mighty one he is, and so is the Gospel, which is the power of God unto salvation; here it seems to design the almighty power of God, displayed in the works of creation and providence; see Isaiah 51:9.
strong is thy hand; thy "left hand", as some, it being distinguished from his right hand, mentioned in the next clause; the Targum adds,
"to redeem thy people;''
the work of redemption was put into the hand of Christ, and it prospered in his hand, and his own arm brought salvation to him; and his hand is strong to keep and preserve his people, where they are put, and where they are safe; and the hand of the Lord is strong to correct and chastise them, and sometimes his hand lies heavy upon them, and presses them sore, when it becomes them to humble themselves under his "mighty hand": and it also strong to punish his and their enemies:
and high is thy right hand; when it is lifted up in a way of judgment against wicked men, and for the defence of his people, then may it be said to be exalted: and it is high enough to reach the highest and most powerful of his adversaries; see Psalm 118:16. The Targum adds,
"to build the house of thy sanctuary.''
Some render (c) these two last clauses as a wish or prayer; "let thy hand be strong, and let thy right hand be lifted up".
(c) So Paginus, Montana, and V. L.