I have heard that the suggestion of Salman Farsi regarding trenches is without sanad. Is this true?
This has been mentioned without objection by reliable Hadith commentators as well as the Seerah biographers, which points to its acceptability according to them.
Some references that mentioned the above:
Seerah Ibn Hisham, Fathul Bari, before Hadith: 4097, ‘Umdatul Qari, before Hadith: 4097 and Al-Bidayah wan Nihayah, vol. 4 pg. 97.
And Allah Ta’ala Knows best,
Answered by: Moulana Muhammad Abasoomar