I came to the Prophet ﷺ with a group from my people, and we stayed with him for twenty nights. He was merciful and gentle, and when he noticed our longing for our families, he said, "Return to them, live among them, teach them, and pray. When the time for prayer comes, let one of you give the call to prayer, and let the eldest among you lead the prayer."
أتيت النبي ﷺ في نفر من قومي، فأقمنا عنده عشرين ليلة، وكان رحيما رفيقا، فلما رأى شوقنا إلى أهالينا قال: ارجعوا فكونوا فيهم وعلموهم وصلوا، فإذا حضرت الصلاة فليؤذن لكم أحدكم، وليؤمكم أكبركم.
Bukhari related it in the chapter on the adhan (628), and Muslim in the chapter on mosques (674), both through Ayub, from Abu Qilaba, from Malik bin Huwayrith, who related the hadith, the wording being Bukhari's. In another wording, he said, "Pray as you have seen me praying, and when the time for prayer comes, let one of you give the adhan, and let the oldest among you lead you in prayer." Bukhari (631).Both of them also related it through Khalid Haddan, from Abu Qilaba, from Malik bin Huwayrith, who said, two men came to the Prophet ﷺ intending to travel, and the Prophet ﷺ said, "When the two of you set out, give the adhan, then give the call to begin the prayer, and then let the older of you two lead the other in prayer." This is how it appears in Sahih Bukhari.In Sahih Muslim it reads, I came along with a companion of mine, and when we wanted to take our leave from him, he said to us, and then he related the hadith in similar fashion.For the rest of the hadiths, see the chapter on the recommendation of giving the adhan for one who prays alone.