9 Before the scattering of the people at the tower of Babel, the world was unified by one language; but it was a world of rebellious people. In contrast, a new purified language will characterize a responsive people (cf. Ro 15:6). The lips or language that had become impure through use in idol worship will become purified so that all may in unison call on the name of the Lord. The reference to lips, the organ of speech, includes the heart behind the language; as Keil, 156, notes, “Purity of the lips involves or presupposes the purification of the heart.” The outpouring of the Holy Spirit on the day of Pentecost brought about purification and renewal of heart and lips resulting in a widespread calling on the name of the Lord (Ac 2:21).
To “call on [qārāʾ] the name of the Lord” is to turn to the Lord out of a sense of need (TWOT, 2:810). Again, this kind of language may refer back to the preflood period (cf. Ge 4:26). The original unity of speech lost at Babel (11:1–9) will ultimately be restored so that all creation may worship God. Those of purified speech are enabled to serve “shoulder to shoulder” (lit., “one shoulder”; cf. Jer 32:39). In a similar vein, the expression “one mouth” is used to indicate unanimity in 1 Kings 22:13.
The Expositor’s Bible Commentary
Conversion of the Remaining Nations (3:9)
The pure language of verse 9 probably does not refer to a universal tongue but rather to lips that are undefiled by idolatry, or to speech that is pure with praise to Jehovah. All peoples will serve Him with one accord.
Believers Bible Commentary
3:9 purified lips. See Introduction: Interpretive Challenges. A remnant of the nations, converted to the Lord, will worship Him in righteousness and truth (Zec 8:20–23; 14:16). Pure speech will come from purified hearts (cf. Lk 6:45).
MacArthur Study Bible
3:9 In that day, God will alter the speech (or lips) of the peoples gathered to be punished (Isa. 6:5–7). The nations had polluted speech, worshiping pagan gods, but now they will have pure speech (cf. Ps. 24:4), cleansed to call upon the name of the Lord in worship (Gen. 4:26). (Some have suggested that this may also allude to the reversal of the Babel syndrome in Gen. 11:1–9.) Worship is not only through word but also through deed, since the nations will serve him. The term ‘abad (“work, serve”) designates obedient work for God (Mal. 3:14). This service is universal, done by all, and unanimous, “with one accord” (cf. 1 Kings 22:13).
ESV Study Bible
3:9 change … a pure speech. To purify the lips is either to cleanse from sin in general (Is. 6:5) or to remove the names of foreign gods from the lips of a worshiper (Hos. 2:17).
of the peoples. The Gentiles will also call on His name (Is. 52:15; 65:1; 66:18).
all of them may call upon the name of the Lord. In contrast with the idolaters of 1:5, 6. See Gen. 4:26; 1 Kin. 18:24; Jer. 10:25; Joel 2:32; Acts 2:21; Rom. 10:12, 13.
Reformation Study Bible