Abrogating the Rule Established by Ijma’a al-Sahaba is Prohibited
Bismillah al-Rahman al-Raheem
Abrogating the Rule Established by Ijma’a al-Sahaba is prohibited
The Shari’ah rule established by Ijma’a al-Sahaba cannot be abrogated because the Ijma’a occurred after the departure of the Messenger of Allah (saw) and its abrogation must take place through the Book or the Sunnah or through an Ijma’a or a Qiyas, and in all of these cases the abrogation would be invalid.As for an abrogation of the text, it would be invalid because the text precedes the Ijma’a; all the texts are received from the Messenger of Allah (saw) and the Ijma’a could not have been established during his lifetime because if he had not agreed with them, it could not have been established and if he had agreed with them, then his saying would have been the evidence. Hence, the proof has been established that the text always preceded the Ijma’a; consequently, it is impossible for the text to abrogate Ijma'a al-Sahaba.
As for the Ijma'a itself, it cannot abrogate another Ijma’a because it is impossible for it to be established differently from another Ijma’a. Had the Ijma’a been established, one of the two Ijma’ain would have been wrong for certain, because if it had not been based on evidence it would have been wrong, because Ijma'a al-Sahaba reveals an evidence; and if it had been based on an evidence, the second one would have been wrong because it would not have been deemed as an Ijma’a since it had been established contrary to the evidence.
As for al-Qiyas, it cannot abrogate an Ijma’a because it would not be sound if it were contrary to the Ijma’a; this is because al-Qiyas is a branch of a root, thus if it transpires that there exists an evidence from the Book or the Sunnah or Ijma'a al-Sahaba which is contradictory to al-Qiyas, then al-Qiyas should be dropped. Hence, since al-Qiyas could not be sound if it were contrary to Ijma'a al-Sahaba, then Ijma'a al-Sahaba could not abrogated by al-Qiyas.
Source: Islamic Personality Volume III