Sahih Muslim 2261a

Abu Salama reported: I used to see dreams (and was so much perturbed) that I began to quiver and have temperature, but did not cover myself with a mantle. I met Abu Qatada and made a mention of that to him. He said: I heard Messenger of Allah ﷺ as saying: A good vision comes from Allah and a (bad) dream (hulm) from devil. So when one of. you sees a bad dream (hulm) which he does not like, he should spit on his left side thrice and seek refuge with Allah from its evil; then it will not harm him.

حَدَّثَنَا عَمْرٌو النَّاقِدُ، وَإِسْحَاقُ بْنُ إِبْرَاهِيمَ، وَابْنُ أَبِي عُمَرَ، جَمِيعًا عَنِ ابْنِ عُيَيْنَةَ، - وَاللَّفْظُ لاِبْنِ أَبِي عُمَرَ - حَدَّثَنَا سُفْيَانُ، عَنِ الزُّهْرِيِّ، عَنْ أَبِي سَلَمَةَ، قَالَ كُنْتُ أَرَى الرُّؤْيَا أُعْرَى مِنْهَا غَيْرَ أَنِّي لاَ أُزَمَّلُ حَتَّى لَقِيتُ أَبَا قَتَادَةَ فَذَكَرْتُ ذَلِكَ لَهُ فَقَالَ سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ " الرُّؤْيَا مِنَ اللَّهِ وَالْحُلْمُ مِنَ الشَّيْطَانِ فَإِذَا حَلَمَ أَحَدُكُمْ حُلْمًا يَكْرَهُهُ فَلْيَنْفُثْ عَنْ يَسَارِهِ ثَلاَثًا وَلْيَتَعَوَّذْ بِاللَّهِ مِنْ شَرِّهَا فَإِنَّهَا لَنْ تَضُرَّهُ " .