Sahih Bukhari: Hadith 6771

Allah's Messenger (ﷺ) 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 prophetism can never be false." Muhammad bin Seereen 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."