Thomas Aquinas Commentary Isaiah 12

I will confess. Here, the thanksgiving for the benefit they received is presented. The prophet, by the prophetic spirit, already saw this benefit and promised it to the people. Therefore, he does three things:

• First, he sings a song.
• Second, he promises the benefit to the people: you will draw waters (Isaiah 12:3).
• Third, he foretells that the people will sing: and you will say (Isaiah 12:4).

At that time, they were oppressed by three evils: divine wrath for past faults, fear of enemies for future punishments, and sorrow of heart for present evils.

Against the first evil, he recalls the mercy of God. Therefore he says, I will confess to you, O Lord, from now on—that is, I will praise you, for the people do not yet see the benefit for which he gives thanks. This is because of what follows: for, at first justly, you were angry with me because of my sins, and your wrath is turned into mercy, and you have comforted me. He speaks of the effect of mercy, using the past tense for the future. This concerns the return of the people from Babylon and, most of all, the consolation accomplished through Christ: As I purposed to afflict you, when your fathers had provoked me to wrath, says the Lord, and I had no mercy: so turning again I have thought in these days to do good to the house of Judah, and Jerusalem (Zechariah 8:14–15).

Against the second evil, he professes confidence in God: Behold, God is my savior, who frees the people from the slavery of Babylon, or more accurately, who will save his people: for he will save his people from their sins (Matthew 1:21); Do not fear, my servant Jacob, says the Lord, nor be dismayed, O Israel: for behold, I will save you from a distant country (Jeremiah 30:10).

Against the third evil, he points to the power of divine strength: my strength, by which I am sustained, and my praise, whom I praise, having abandoned idols: I will love you, O Lord, my strength (Psalms 18:1).

You will draw. Here he promises the benefit: waters of comfort, cooling them from the heat of tribulation.

And you will say. Here he foretells that the people will also sing after the benefit has been received. This section contains the people's mutual exhortation to divine praise. An exhortation to three things is presented:

• to the confession of divine praise,
• to thanksgiving: sing to the Lord (Isaiah 12:5),
• to shared rejoicing: rejoice (Isaiah 12:6).

Concerning the first, four things are presented:

• We either confess the Lord through faith: confess the Lord. For with the heart, we believe unto justice; but, with the mouth, confession is made unto salvation (Romans 10:10).
• Or we call upon him through prayer: and call upon him. As it says below: Seek the Lord, while he may be found; call upon him, while he is near (Isaiah 55:6).
• Or he is announced through preaching: make his works known, for he does many things to save them. Hear the word of the Lord, O you nations, and declare it in the distant islands (Jeremiah 31:10).
• Or he is remembered through continual meditation: remember. Remember his marvelous works (Psalms 105:5).

Sing to the Lord. Here he exhorts them to thanksgiving.

• First, that they give thanks to God: sing to the Lord, for he has done great things in freeing us. Sing to the Lord a new song, because he has done wonderful things (Psalms 98:1).
• Second, that it be announced to the world: show this forth in all the earth. Bless the God of heaven, give glory to him in the sight of all that live .

Rejoice. Here the exhortation to exultation is presented.

• First, that there be joy in their hearts: rejoice.
• Second, that there be songs of joy on their lips: praise.
• Third, the reason for both is given: for great is he. As it says below: it will rejoice with joy and praise (Isaiah 35:2).

It should be noted regarding the words, you will draw waters (Isaiah 12:3), that there is:

• First, the water of doctrine, as it says below: All you that thirst, come to the waters (Isaiah 55:1).
• Second, the water of grace: He who believes in me, out of his belly will flow rivers of living water (John 7:38).
• Third, the water of baptismal purity: Unless a man is born again of water and the Holy Spirit, he cannot enter into the kingdom of God (John 3:5).

Likewise, note that water is drawn from the fountain:

• First, from the fountain of divine wisdom: The word of God on high is the fountain of wisdom .
• Second, from the fountain of eternal life: They have forsaken me, the fountain of living water (Jeremiah 2:13).
• Third, from the body of Christ: In that day there will be a fountain opened to the house of David (Zechariah 13:1).

Note on the words, his worksAdinventiones. (Isaiah 12:4), that Christ devisedAdinvenit.:

• First, a brief word of salvation: He devised all the way of knowledge, and gave it to Jacob his servant, and to Israel his beloved .
• Second, a new mode of salvation: I have found wherein I may be merciful to him (Job 33:24).
• Third, a people to be saved: Rejoice with me, because I have found the coin which I had lost (Luke 15:9).

Note on the words, in your midst, the Holy One of Israel (Isaiah 12:6), that Christ is in our midst:

• First, as a light to illuminate: He shone in his days as the morning star in the midst of a cloud .
• Second, as a mediator to reconcile: Jesus stood in the midst of the disciples and said to them: Peace be with you (Luke 24:36).
• Third, as a servant to distribute: But I am in the midst of you, as one who serves (Luke 22:27).