Isaiah 48:3
I have declared the former things from the beginning; and they went forth out of my mouth, and I shewed them; I did them suddenly, and they came to pass. I have declared the former things from the beginning; and they went forth out of my mouth, and I shewed them; I did them suddenly, and they came to pass.
God declared the former things from the beginning, spoke them forth out of His mouth, showed them, and then did them suddenly so that they came to pass. He announced those events beforehand and fulfilled them suddenly so that their fulfillment could not be credited to idols. The word is spoken to the house of Jacob called by the name of Israel and come forth out of the waters of Judah, who swear by the name of the Lord and make mention of the God of Israel but not in truth nor in righteousness, who call themselves of the holy city and stay themselves upon the God of Israel. The chapter warns of the condition of those who have had truth line upon line and precept upon precept, repeatedly receiving truth, yet refuse to hear and receive His testimonies of warning. In refusing, they hinder His work and cause with misrepresentation, falsehood and heresy, and dismiss the speaking of His Spirit as nothing.
The verse belongs with Isaiah 48 through 52, which show the appointed work to be done now and must be studied carefully with willingness to do His bidding. It calls for united and determined effort with no delay, for decided work in the cities, for an increase of workers to meet the demands of the work, and for means to be brought in to carry forward soul-saving and to proclaim the message throughout the world. It calls for girding on the armor, and for reconsecration and harmony with the Lord God and with Christ His only begotten Son. It calls lay members who have means to remember their responsibility to help without delay, to resist Satan's temptation to enter commercial enterprises, and instead to invest their means in the Lord's work.