Muwatta Imam Malik Book of Asking for Rain, Hadith 5

Yahya related to me from Malik that he had heard that the Messenger of Allah ﷺ used to say, "When a cloud appears from the direction of the sea and then goes towards ash-Sham, it will be an abundant source of rain."

وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يَقُولُ " إِذَا أَنْشَأَتْ بَحْرِيَّةً ثُمَّ تَشَاءَمَتْ فَتِلْكَ عَيْنٌ غُدَيْقَةٌ " .