Isaiah 40:2

It is a good sign that mercy is preparing for us if we find God's grace preparing us for it, Ps. x. But it must be applied to John the Baptist; for, though God was the speaker, he was the voice of one crying in the wilderness, and his business was to prepare the way of the Lord, to dispose men's minds for the reception and entertainment of the gospel of Christ.

Double for all her sins “Blessings double to the punishment” - It does not seem reconcilable to our notions of the Divine justice, which always punishes less than our iniquities deserve, to suppose that God had punished the sins of the Jews in double proportion; and it is more agreeable to the tenor of this consolatory message to understand it as a promise of ample recompense for the effects of past displeasure, on the reconciliation of God to his returning people.

Messiah is the antitypical Israel (compare Mt 2:15, with Ho 11:1). He indeed has "received" of sufferings amply more than enough to expiate "for our sins" (Ro 5:15, 17). Otherwise (cry unto her) "that she shall receive (blessings) of the Lord's hand double to the punishment of all her sins" (so "sin" is used, Zec 14:19, Margin) [LOWTH].

Speak ye comfortably - Hebrew, על־לב ‛al-lēb as in the margin, ‘To the heart.’ The heart is the seat of the affections. It is there that sorrow and joy are felt. We are oppressed there with grief, and we speak familiarly of being pained at the heart and of being of a glad or merry heart. To speak ‘to the heart,’ is to speak in such a way as to remove the troubles of the heart; to furnish consolation, and joy. It means that they were not merely to urge such topics as should convince the understanding, but such also as should be adopted to minister consolation to the heart. So the word is used in Gen 34:3: ‘And his soul clave unto Dinah - and he loved the damsel, and spake kindly (Hebrew, to the heart) of the damsel;’ Gen 50:21: ‘And he comforted them, and spoke kindly unto them’ (Hebrew, to their hearts); see also 2Ch 32:6. To Jerusalem - The direction is not merely to speak to the people in Babylon, but also to comfort Jerusalem itself lying in ruins. The general direction is, therefore, that the entire series of topics of consolation should be adduced - the people were to return from their bondage, and Jerusalem was to be rebuilt, and the worship of God to be restored. And cry unto her - In the manner of a crier; or one making public and loud proclamation (compare Isa 40:3, Isa 40:9). Jerusalem is here personified. She is addressed as in ruins, and as about to be rebuilt, and as capable of consolation from this promise. That her warfare is accomplished - Septuagint, ‘That her humiliation (ταπείνωσις tapeinōsis) is accomplished.’ The Hebrew word (צבא tsâbâ', ‘warfare’) properly means an army or host (compare the note at Isa 1:9), and is usually applied to an army going forth to war, or marshalled for battle 2Sa 8:16; 2Sa 10:7. […]