Is the hadith that states the companions used to close their gatherings with Sura al-Asr weak? If so, can we act up it?”
The hadith at hand is found in the Sunan of Imam Abu Dawod (417) and the M’ujam al-Aawsat of Imam al-Tabarani (5124) on behalf of Abu Madaniyah al-Darami who says:
“If two men from the companions of the Prophet [may peace and blessing of Allah be upon him] met, the would not part until they recited surah al-Asr, then they would give each other the greetings.”
Ibn Hajar al-Hathami says in Majm’u al-Fawaid vol. 4 pg. 463 and vol. 10 pg. 233, “The narrators of this hadith are all sound.”
In addition, this hadith was authenticated by Sh. Albani in his collection of sound narrations #2648.
There is difference amongst the scholars on acting on weak hadith. This difference is well known and accepted amongst the major scholars of hadith. Here is an article by Ust. Jamal Diwan on the subject. The point is that, even if the hadith was weak, there should be non censuring of those who act upon it unless it fails to meet the conditions outlined by Ust. Jamal in his translations. Click here for the article.
Allah knows best