"In the lifting up of hands, allusion is made to praying and vowing; and [the psalmist] intimates, that besides giving thanks to God, [they] would acquire additional confidence in supplication, and be diligent in the exercise of it. Any experience we may have of the divine goodness, while it stirs us up to gratitude, should, at the same time, strengthen our hopes of the future, and lead us confidently to expect that God will perfect the grace which he has begun."
I like the way Calvin moves from the lifting up of hands to the perfection of the grace begun. To lift one's hands is a sign of surrender, a sign of giving, and an invitation to weakness—for the raising of one's arms can't help but sap our strength. This threefold meaning of the lifting of hands therefore lends itself to the idea of sanctification, for perfection cannot occur without surrender, without giving all I have, and without a realization that in my weakness, I will discover God's strength.
I lift up my hands to you, O God, in prayer, in surrender, in invitation to make you my all in all. Amen.