He literally believes that inflation is caused by high interest rates, because he thinks that the Quran says so. [0] This is a common belief among a certain crazy subset of islamic economics, but to be clear, is not mainstream belief among Muslims.
Does Erdogan believe that the Quran says inflation is caused by high interest rates? That would be fascinating if true.
However, the article you cited does not make that claim. It merely says that Erdogan is opposed to high interest rates because they are considered "usury" and are thus forbidden. This is different from saying that high interest rates cause inflation.
Do you have a different source specifically for the claim that the some people think Quran indicates that high interest rates cause inflation?
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.
[0]: https://www.spectator.co.uk/article/islamonomics-how-erdogan...