Surah At-Tur, ayah 38

أَمۡ لَهُمۡ سُلَّمٞ يَسۡتَمِعُونَ فِيهِۖ فَلۡيَأۡتِ مُسۡتَمِعُهُم بِسُلۡطَٰنٖ مُّبِينٍ ٣٨

Am lahum sullamun yastami'ūna fīhi falya'ti mustami'uhum bisultānim mubīn

Or have they a stairway [into the heaven] upon which they listen? Then let their listener produce a clear authority [i.e., proof].