Isaiah 48:7

5 Therefore I declared it to you long ago; I announced it before it came to pass, so that you could not claim, ‘My idol has done this; my carved image and molten god has ordained it.’

6 You have heard these things; look at them all. Will you not acknowledge them? From now on I will tell you of new things, hidden things unknown to you.

They are created now, and not long ago; you have not heard of them before today. So you cannot claim, ‘I already knew them!’

8 You have never heard; you have never understood; for a long time your ears have not been open. For I knew how deceitful you are; you have been called a rebel from birth.

9 For the sake of My name I will delay My wrath; for the sake of My praise I will restrain it, so that you will not be cut off.

This was said to Israel at a particular time, so it is wise to read it together with the surrounding text. Do read the surrounding verses too, because the context often says more than a single verse.

Compare

BSB
They are created now, and not long ago; you have not heard of them before today. So you cannot claim, ‘I already knew them!’
KJV
They are created now, and not from the beginning; even before the day when thou heardest them not; lest thou shouldest say, Behold, I knew them.
WEB
They are created now, and not from of old. Before today, you didn’t hear them, lest you should say, ‘Behold, I knew them.’
ASV
They are created now, and not from of old; and before this day thou heardest them not; lest thou shouldest say, Behold, I knew them.
DARBY
they are created now, and not long ago; and before this day thou hast not heard them, lest thou shouldest say, Behold, I knew them.
BLB
Now they have been created, and not from then; and before this day, and you did not hear of them, lest you should say, ‘Behold, I knew them.’
ÅB
Nå først er det skapt, og ikke for lenge siden, og før idag hadde du ikke hørt det, for at du ikke skulle si: Det visste jeg!
OTB
De er skapt nå, og ikke for lenge siden; du har ikke hørt om dem før i dag, så du ikke kan si, 'Ja, jeg visste dem.'
B1930
Nu først er det skapt, og ikke for lenge siden, og før idag hadde du ikke hørt det, forat du ikke skulde si: Det visste jeg!

Study notes (Tyndale)

Original text and word study