this headline is the closest thing in it he says:
'... and they are complaining about cutting the interest rates. Don't expect anything different from me. As a muslim, I'll continue doing what the religion/quran orders me to do. This is the ruling (of the religion).'
That seems to, again, say that Erdogan believes high interest rates are forbidden under Islamic law; but that is different than saying that the Quran says high interest rates cause inflation (as the parent claimed Erdogan believed).
To be clear, I don't hold the position that Erdogan doesn't believe high interest rates cause inflation -- I don't know what he believes. I am just trying to find a source that backs up the parents' claim, if there is one.
https://www.birgun.net/haber/erdogan-bir-musluman-olarak-nas...
this headline is the closest thing in it he says: '... and they are complaining about cutting the interest rates. Don't expect anything different from me. As a muslim, I'll continue doing what the religion/quran orders me to do. This is the ruling (of the religion).'