Adam Clarke on Isaiah 12

Though thou wast angry "For though thou hast been angry" - The Hebrew phrase, to which the Septuagint and Vulgate have too closely adhered, is exactly the same with that of St. Paul, Rom 6:17 : "But thanks be to God, that ye were the slaves of sin; but have obeyed from the heart;" that is, "that whereas, or though, ye were the slaves of sin, yet ye have now obeyed from the heart the doctrine on the model of which ye were formed."

The Lord Jehovah - The word יה Yah read here is probably a mistake; and arose originally from the custom of the Jewish scribes, who, when they found a line too short for the word, wrote as many letters as filled it, and then began the next line with the whole word. In writing the word יהוה Jehovah, the line might terminate with יה Yah, the two first letters; and then at the beginning of the next line the whole word יהוה Yehovah would be written. This might give rise to יה יהוה Yah Yehovah. The Yah is wanting here in two of Dr. Kennicott's MSS., in one ancient MS. of my own, and in the Septuagint, Vulgate, Syriac, and Arabic. See Houbigant and De Rossi.

My song - The pronoun is here necessary; and it is added by the Septuagint, Vulgate, and Syriac, who read זמרתי zimrathi, as it is in a MS. Two MSS. omit יה Yah, see Houbigant, not. in loc. Another MS. has it in one word, זמרתיה zimrathyah. Seven others omit יהוה Yehovah. See Exo 15:2, with Var. Lect. Kennicott.

Call upon his name - קראו בשמו kiru bishmo, invoke his name. Make him your Mediator, or call the people in his name. Preach him who is the Root of Jesse, and who stands as an ensign for the nations. Call on the people to believe in him; as in him alone salvation is to be found.

Thou inhabitant of Zion - Not only the Jewish people, to whom his word of salvation was to be sent first; but also all members of the Church of Christ: as in them, and in his Church, the Holy One of Israel dwells. St. Paul, speaking of the mystery which had been proclaimed among the Gentiles, sums it up in these words:" which is Christ in You, the hope of glory; whom we preach, warning every man, and teaching every man in all wisdom, that we may present every man perfect in Christ Jesus;" Col 1:27, Col 1:28. Well, therefore, may the inhabitant of Zion cry oat and shout, and proclaim the greatness of her Redeemer.