I was pointing at a thundercloud and saying that lightning may strike, and my Chinese friend said a 4-syllable phrase that meant that it happened just as I finished talking about it.
Do you know this phrase?
In Cantonese, it is "話口未完" wa6 hau2 mei6 yun4.
In Mandarin, perhaps "話還沒說完”,hua4 hai2 mei2 shuo1 wan2, but then it is five syllable, not four.
一语成谶 (yī yǔ chéng chèn)
Iciba: 一语成谶
一语成谶
fits OP's requirement, it just means someone said something, and then (maybe after a long time, not immediately) it became true. And note that 一语成谶
only used for bad things.
It is not easy guessing what that phrase is without knowing whether it is Mandarin or Cantonese. In Cantonese it could be the colloquial 一講曹操 referring to 一講曹操,曹操就到. Its English equivalence is speak of the devil.
(I'm not sure if in Mainland/Taiwan Mandarin whether people just use the first half as 方說曹操 or 一講曹操 etc.)
话音未落
?