I just have a quick question. While I was praying after rising form bowing, I said accidentally : rabanaa wallakal ham instead of hamd Do you know if this makes a prayer invalid or do you have to redo it?
Also during prayer if you mispronounce something in a minor way do you have to repeat it?
Allah knows what the hearts conceal 17:25, 64:4 and what one intends 2:177, 2:225, 7:29. Salah is for Allah's remembrance 20:14. So long as one knows what he's saying 4:43 and he remembers Allah it shouldn't matter how it sounds to others. We should not be praying to show off because this is one of the traits of the munafiqin, 107:4-6.
There is no indication from what the Qur'an says or any hadith from the Prophet which nullifies prayer due to mispronunciation. Whoever claims such then he must prove it.
A mis-pronunciation doesn't break the Salah unless that changes the total meaning of the word and means something opposite which contradicts the Quran. As for your case, you Salah was fine and you wouldn't need to repeat your Salah because of that. But yah, if someone says something like I explained at first, then the Salah is incomplete and the person should repeat it.
Mispronouncing "rabbanaa (wa) lakal hamd" doesn't invalidate the prayer since it's not something fard to say. You don't have to repeat the prayer either.