After rain has fallen
Allah says that morning divides people into two, by one sentence.
أَصْبَحَ مِنْ عِبَادِي مُؤْمِنٌ بِي وَكَافِرٌ، فَأَمَّا مَنْ قَالَ مُطِرْنَا بِفَضْلِ اللَّهِ وَرَحْمَتِهِ فَذَلِكَ مُؤْمِنٌ بِي وَكَافِرٌ بِالْكَوْكَبِ، وَأَمَّا مَنْ قَالَ بِنَوْءِ كَذَا وَكَذَا فَذَلِكَ كَافِرٌ بِي وَمُؤْمِنٌ بِالْكَوْكَبِ
Muṭirnā bi-faḍli-llāhi wa raḥmatih.
“We have been given rain by the grace of Allah and His mercy.”
The narration contrasts it with saying we were given rain by such-and-such a star. The water is identical. What differs is who you think sent it.
The full narration
Narrated Zaid bin Khalid Al-Juhani:The Prophet (ﷺ) led us in the Fajr prayer at Hudaibiya after a rainy night. On completion of the prayer, he faced the people and said, "Do you know what your Lord has said (revealed)?" The people replied, "Allah and His Apostle know better." He said, "Allah has said, 'In this morning some of my slaves remained as true believers and some became non-believers; whoever said that the rain was due to the Blessings and the Mercy of Allah had belief in Me and he disbelieves in the stars, and whoever said that it rained because of a particular star had no belief in Me but believes in that star
Source
Ṣaḥīḥ al-Bukhārī · 846
- Agreed upon as authentic (al-Bukhārī / Muslim)