Abu Hurayrah (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "Angels do not accompany a group of travelers who have with them a dog or a bell."
شرح الحديث :
If a group of people set out for a journey and they have a dog or a bell with them, then the angels of mercy and seeking forgiveness will not accompany them on their journey. That is because a dog is impure, and as for a bell, it is one of the musical instruments of Satan, as the Prophet (may Allah's peace and blessings be upon him) has informed us. Some scholars have restricted the prohibition to the bell that is hung on animals' necks, as it produces a melodious sound that impresses the people and causes them to find pleasure in hearing it. For this reason, the Prophet (may Allah's peace and blessings be upon him) called the bell the musical instrument of Satan. As for the alarm sound in watches or clocks and the like, they are not included in this prohibition, because they are not hung on animals, and are only made to ring at specific times. The same applies to doorbells which are used for seeking permission to enter. There is no problem with these bells and they are not prohibited, because they are not hung on animals, or whatever is like animals, and there is no pleasure in hearing them, for which the Prophet (may Allah's peace and blessings be upon him) has prohibited it.