Zechariah 4:6

4:6 Therefore he told me, “These signify the word of the Lord to Zerubbabel: ‘Not by strength and not by power, but by my Spirit,’ ¹  says the Lord who rules over all.”

Zechariah 12:5

12:5 Then the leaders of Judah will say to themselves, ‘The inhabitants of Jerusalem are a means of strength to us through their God, the Lord who rules over all.’

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¹ sn It is premature to understand the Spirit here as the Holy Spirit (the third Person of the Trinity), though the OT prepares the way for that NT revelation (cf. Gen 1:2; Exod 23:3; 31:3; Num 11:17-29; Judg 3:10; 6:34; 2 Kgs 2:9, 15, 16; Ezek 2:2; 3:12; 11:1, 5).