Narrated from Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "The angels do not accompany a group of travelers among whom there is a dog or a bell." __QUR_N__ Imam Tirmidhi says: 1- This hadith is hasan sahih, 2- In this chapter, there are also ahadith from 'Umar, 'Aishah, Umm Habibah, and Umm Salamah (may Allah be pleased with them all).
Shaykh Dr. Abdur Rahman Freywai
Explanation: 1: Such dogs that are used for hunting or guarding are exempt from this ruling. Hanging a bell around a horse’s neck informs the enemy about the presence of the horse’s owner; therefore, it has been disliked. And by “bell” is meant anything that, when hung around the animal’s neck, produces sound with movement.
Source: Sunan al-Tirmidhi – Majlis ‘Ilmi Dar al-Da‘wah, New Delhi Edition, Page: 1703