[CoenceLomneedtrue]

Ayah from Surah Yaseen

وَجَعَلْنَا مِنْ بَيْنِ أَيْدِيهِمْ سَدًّا وَمِنْ خَلْفِهِمْ سَدًّا فَأَغْشَيْنَاهُمْ فَهُمْ لَا يُبْصِرُونَ

"Wa Ja'alna Mim Bayna Aydeehim Saddanw Wa Min Khalfihim Saddan Fa Aghshaynahum Fa Hum La Yubsiroon"

And We have put a barrier before them, and a barrier behind them, and We have covered them up, so that they cannot see.

This is what Rasulullah read and blew unto the sand which he then threw in the direction of the assassins who were waiting outside his house. They could not see anything.

I've personally seen this du'aa work twice.