You don’t say it in your heart. You simply intend it.

I know saying intention out is bidah but I am confused how one should keep intentions just in heart when praying. For salah should I just think that ok i m going to pray 2 fardh, etc or do I need to say in heart that now I am going to pray 2 fardh of fajr for the sake of ALLAH or something such?

Prayer |