From Ibn ʿUmar (may Allah be pleased with them both), who said: The Messenger of Allah (ﷺ) said: "If people knew what I know about travelling alone, no rider would journey by night on his own." Narrated by al-Bukhārī.
١٦٧ - باب استحباب طلب الرفقة وتأميرهم على أنفسهم واحدا يطيعونه
From Ibn ʿUmar (may Allah be pleased with them both), who said: The Messenger of Allah (ﷺ) said: "If people knew what I know about travelling alone, no rider would journey by night on his own." Narrated by al-Bukhārī.
From ʿAmr b. Shuʿayb, from his father, from his grandfather (may Allah be pleased with him), who said: The Messenger of Allah (ﷺ) said: "A single rider is a devil, two riders are two devils, and three are a [proper] travelling party." Narrated by Abū Dāwūd, al-Tirmidhī, and al-Nasāʾī with sound chains of narration; and al-Tirmidhī said: "A good (ḥasan) hadith."
From Abū Saʿīd and Abū Hurayra (may Allah, exalted be He, be pleased with them both), who said: The Messenger of Allah (ﷺ) said: "When three set out on a journey, let them appoint one of them as leader." A good (ḥasan) hadith, narrated by Abū Dāwūd with a good chain of narration.
From Ibn ʿAbbās (may Allah be pleased with them both), from the Prophet (ﷺ), who said: "The best of companions are four; the best of detachments are four hundred; the best of armies are four thousand; and twelve thousand will never be overcome on account of small numbers." Narrated by Abū Dāwūd and al-Tirmidhī, who said: "A good (ḥasan) hadith."