Albert Barnes Commentary Isaiah 9:3

"Thou hast multiplied the nation, thou hast increased their joy: they joy before thee according to the joy in harvest, as men rejoice when they divide the spoil." — Isaiah 9:3 (ASV)

Thou hast multiplied the nation - You have made the nation strong, powerful, and mighty. Several interpreters, such as Calvin, Vitringa, and Le Clerc, suppose that the prophet here, and in the two following verses, speaks in the first instance of the prosperity near at hand, and of the rapid increase of the Israelites after the return from the Babylonian exile. The inhabitants of Galilee must have participated in this increase, as may be inferred from the accounts of Josephus regarding the great population of that province in his time (see Jewish Wars, i. 20, 23).

Vitringa also directs our attention to the fact that the Jewish people, after the exile, not only filled Judea but also spread into Egypt, Syria, Mesopotamia, Asia Minor, Greece, and Italy. However, it seems unnecessary to refer it to such an increase of the inhabitants. It may refer to the great increase of the Messiah’s kingdom, or of the kingdom He would establish, whose commencement would be in Galilee (see Hengstenberg, Christology, vol. 1, p. 354).

And not increased the joy - The Masoretes here read in the margin לו (lô), “to it,” instead of לא (lo'), “not.” Eleven manuscripts, two of them ancient, have this reading. This reading is followed by the Chaldee Paraphrase, the Syriac, and the Arabic. The Septuagint also seems to have understood it this way. This is also the reading in the margin, the connection demands it, and it is unquestionably the correct reading.

It would then read, “Thou hast increased for it (the nation) the joy.” Hengstenberg, however, suggests that the phrase may mean, “whose joy you did not previously enlarge,” that is, “upon whom you had previously inflicted heavy sufferings.” But this interpretation is harsh, and I see no reason to doubt that an error may have crept into the text.

They joy before thee according to the joy of harvest - This is a beautiful figure and is found frequently in ancient writings. The harvest was a time of exultation and joy, commonly gathered amid songs and rejoicings, and concluded with a festival. The phrase “before thee” refers to the fact that the first-fruits of the harvest among the Hebrews were presented with thanksgiving before God in the temple (Deuteronomy 12:7; Deuteronomy 14:22–26).

And as men rejoice ... - This is also an expression of great joy and rejoicing. Such an occasion, at the close of a battle when great spoil or plunder had been taken, would be a time of great rejoicing (1 Samuel 30:16; 2 Chronicles 20:25–28).