“Glory be to him whom you glorified.” He said that the thunderclap is an angel who yells at the rainclouds as a shepherd yells at his sheep/goats.  

سَمِعَ صَوْتَ الرَّعْدِ قَالَ سُبْحَانَ الَّذِي سَبَّحْتَ لَهُ قَالَ إِنَّ الرَّعْدَ مَلَكٌ يَنْعِقُ بِالْغَيْثِ كَمَا يَنْعِقُ الرَّاعِي بِغَنَمِهِ  

“Glory be to him whose praise the thunderclap sings and the angels glorify in awe of him”. He used to say, then, that the thunder-clap is a stern warning for the dwellers of earth.  

سَمِعَ الرَّعْدَ تَرَكَ الْحَدِيثَ وَقَالَ سُبْحَانَ الَّذِي {يُسَبِّحُ الرَّعْدُ بِحَمْدِهِ وَالْمَلاَئِكَةُ مِنْ خِيفَتِهِ} ثُمَّ يَقُولُ إِنَّ هَذَا لَوَعِيدٌ شَدِيدٌ لأهْلِ الأرْضِ