ってば

Etymology
In modern Japanese, an emphasis of, itself a contraction of , from quotative particle and the conditional conjugation  of verb.

Literally means, “if that's what [someone] says / said”. Also used idiomatically to mean something along the lines of, “if that's what [I / you / someone] said, then [that's what I really mean / why won't you agree with me]”.

Usage notes
Becomes if preceded by a word ending with.