Why the word Al-Saabi'oon is in the nominative form in verse 5:69
18-10-2015 | IslamWeb
Question:
I would like to know about the grammar of the word Al-Saabi’oon in Soorat al-Maa’idah. Why does it appear in the nominative form (Al-Saabi’oon) while it appears in the accusative (Al-Saabi’een) in another soorah although the syntax is very similar in both passages?
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
There are different opinions regarding the reason for using the word As-Saabi’oon, meaning the Sabians, in verse 5:69 in the nominative form, and the preponderant opinion is that it is used in the nominative form because it is a mubtada' (the subject of a sentence) at the beginning of a nominal sentence. It was the tradition of the Arabs, when they used the particle 'inna' for affirmation purposes and mentioned its subject (ism inna) and predicate (khabar inna) and then wished to use a conjunction ('atf) to conjoin its subject to another subject that is alien to that context, that they would use that other subject in the nominative case in order to indicate that the intent was to connect the sentences together, and not the individual words. Given that the Sabians were more deviant from the Truth compared to the Jews and Christians in the Jaahiliyyah (the pre-Islamic era of ignorance) because they worshiped the stars - yet they were among those who were offered the chance of salvation if they were to choose to believe in Allaah and the Last Day and act upon that faith - the word As-Saabi’oon in the verse was used in the nominative form so as to stress this fact.
Ibn ‘Aashoor 
wrote, "The majority of Quran commentators held that the word As-Saabi’oon is used in the nominative form as a mubtada' (subject) and that the predicate is omitted given that it is already indicated by the predicate of the particle 'inna'. They maintained that the wording without the omission would have been as follows: 'Those who believed (Muslims), the Jews, and the Christians shall receive their full rewards ... and the Sabians as well...' Some Quran commentators suggested different potential explanations, which Al-Aloosi summed up in five. The explanation given above is clearer and more suitable to the style and the intended meaning of the verse (than the other explanations)..." [At-Tahreer wat-Tanweer]
Allaah Knows best.