say nothing
I promised not to say anything.
Ela se sentiu tão humilhada que não pôde dizer nada.
She felt so humiliated that she couldn't say anything.
O Tom não se atreveu a dizer nada.
Tom didn't dare say anything.
I promised not to say anything.
I'm not going to tell you anything.
Não soube dizer nada verdadeiro a quem envelheceu ao seu lado!
He couldn't say anything truthful to those who grew old by his side!
— Oito e Meio (1963)
I can't say anything.