Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: A man came to the Prophet (peace and blessings be upon him) and submitted: O Messenger of Allah, I see dreams that make me ill. The Prophet (peace and blessings be upon him) said: "A good dream is from Allah Almighty and a bad dream is from Satan. When one of you sees such a (bad) dream, he should spit lightly to his left three times and seek refuge in Allah from its evil, and then that dream will not harm him."
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains a narrator, Kathir bin Sulaym, who is da'if (weak). Ibn Hibban declared him thiqah (trustworthy), yet he mentioned him in his book al-Du'afa'. And Allah knows best.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب التعبير / 11735