Yahya related to me from Malik that Yahya ibn Said said that he had heard that Khalid ibn al-Walid said to the Messenger of Allah, may Allah bless him and grant him peace, "I have nightmares." The Messenger of Allah, may Allah bless him and grant him peace, said to him, "Say, 'I seek refuge with the complete words of Allah from His anger and His punishment and the evil of His slaves, and from the evil suggestions of the shayatin and from their being present (at death).'"
Audhu bi kalimati' llahi't-tammati min ghadabihi wa iqabihi wa sharri ibadihi wa min hamazati' sh-shayatin wa an yahdurun. MALIK MUWATTA, Book 51, Number 51.4.9
Narrated Abu Huraira:
Allah's Apostle said, "When the Day of Resurrection approaches, the dreams of a believer will hardly fail to come true, and a dream of a believer is one of forty-six parts of prophetism, and whatever belongs to prothetism can never be false." Muhammad bin Sirin said, "But I say this." He said, "It used to be said, 'There are three types of dreams: The reflection of one's thoughts and experiences one has during wakefulness, what is suggested by Satan to frighten the dreamer, or glad tidings from Allah. So, if someone has a dream which he dislikes, he should not tell it to others, but get up and offer a prayer." He added, "He (Abu Huraira) hated to see a Ghul (i.e., iron collar around his neck in a dream) and people liked to see fetters (on their feet in a dream). The fetters on the feet symbolizes one's constant and firm adherence to religion." And Abu 'Abdullah said, "Ghuls (iron collars) are used only for necks." SAHIH AL-BUKHARI, Volume 9, Book 87, Number 144