Shaykh Al-Albânî states in Al-Sahîhah Vol. 1 p300, “[This is] recorded by Al-Bayhaqî Vol. 7 p100 with a sahîh chain of transmission from Al-Sha’bî.”

Abû Madînah Al-Dârimî – Allâh be pleased with him – reports, “When two of the Companions of Allâh’s Messenger – Allâh’s peace and blessings be upon him – would meet, they would not part until one would recite to the other “By time, verily man is in loss…” (Sûrah Al-‘Asr). Then, one of them would say salâm to the other.”

Recorded by Al-Tabarânî in Al-Awsat, and others. Shaykh Al-Albânî graded its chain of transmission sahîh. See Al-Sahîhah, hadîth 2648.

Shaykh Al-Albânî states, “There are two points of benefit in this narration about the practice of our Salaf – Allâh be pleased with them all. The first is that they used to say salâm when parting, which has been explicitly mentioned in some statements of the Prophet…The other, we learn from the regular practice of the Companions, is reciting Sûrah Al-‘Asr [when parting], for we believe that they were the farthest of people from introducing into the religion a worship by which they sought to bring themselves closer to Allâh, except with some sanction from Allâh’s Messenger – peace and blessings be upon him, either through a statement from him, or an action of his, or by his tacit approval…”

More:

1. Supplicating for an Unbeliever
2. The Weight of the Quran
3. How the Salaf studied the Quran
4. Won’t you collect your Share?
5. Ibn Mas’ud on the Companions [with notes on Bid'ah Hasanah]

This is from Sayings of the Salaf - English translations of narrations from the Salaf - the earliest believers, our righteous predecessors, and true scholars of Islam. Selected and translated by Owais Al-Hashimi