Silent prayer of a sincere heart

That's a beautiful and meaningful reminder. Here's how you might express this in Roman transliteration of an Islamic phrase:

"Allah sab sunta hai, dil ki chup si chup dua bhi. Is liye kabhi dua karna chhodo mat, aur apna yakeen Us par rakho."

This reflects the idea that Allah is always listening, even to the most silent prayers, and we should always keep our faith in Him.