The Quran names the Sabians three times and gives no description of them. The two leading identifications, the Mandaeans of southern Iraq and the star-venerating people of Harran, rest on different kinds of evidence and point in different directions, and the Harranian case is complicated by a report that the name was adopted there in order to obtain protected status. The identification has been argued since the ninth century by parties with a legal interest in the answer.
What would resolve this A securely dated pre-Islamic attestation of the name applied to a specific community, or documentary evidence of self-designation from either candidate group before the Abbasid period, would settle it. Failing that, a systematic comparison of the earliest Quranic commentaries against the Mandaean and Harranian source material could establish which identification the earliest readers actually held.
OpenSemitic philology, Quranic exegesis and its history, the archaeology and epigraphy of upper Mesopotamia, and Mandaean studiesDivinity Atlas Open Questions Register, First Edition