What he corrected when the animal stumbled
The rider had said the obvious thing.
لاَ تَقُلْ تَعِسَ الشَّيْطَانُ فَإِنَّكَ إِذَا قُلْتَ ذَلِكَ تَعَاظَمَ حَتَّى يَكُونَ مِثْلَ الْبَيْتِ وَيَقُولَ بِقُوَّتِي وَلَكِنْ قُلْ بِسْمِ اللَّهِ فَإِنَّكَ إِذَا قُلْتَ ذَلِكَ تَصَاغَرَ حَتَّى يَكُونَ مِثْلَ الذُّبَابِ
Lā taqul: taʿisa-sh-shayṭān. Fa-innaka idhā qulta dhālika taʿāẓama ḥattā yakūna mithla-l-bayti wa yaqūla bi-quwwatī. Wa lākin qul: bismi-Llāh. Fa-innaka idhā qulta dhālika taṣāghara ḥattā yakūna mithla-dh-dhubāb
Do not say: may Satan perish. If you say that he swells until he is the size of a house and says, by my power. But say: in the name of Allah. If you say that he shrinks until he is the size of a fly.
Where this comes from
The man was riding behind him and the animal tripped, and he cursed the devil, which sounds like the pious response. He was told it is the opposite. Naming him as the cause is the credit he wants.
The full narration
Abu al-Malih reported on the authority of a man :I was riding on a mount behind the prophet (May peace be upon him). It stumbled. Thereupon I said: May the devil perish! He said: do not say; may the devil perish! For you say that, he will swell so much so that he will be like a house, and say: by my power. But say: in the name of Allah; for when you say that, he will diminish so much so that he will be like a fly
Source
Sunan Abī Dāwūd · 4982
- Al-Albani: Sahih
- Muhammad Muhyi Al-Din Abdul Hamid: Sahih
- Zubair Ali Zai: Isnaad Sahih