Is it that Allah ordered them to differ and they obeyed Him? Or He prohibited them from it but they disobeyed Him? Or (is it that) Allah sent an incomplete Faith and sought their help to complete it? Or they are His partners in the affairs, so that it is their share of duty to pronounce and He has to agree? Or is it that Allah the Glorified sent a perfect faith but the Prophet fell short of conveying it and handing it over (to the people)? The fact is that Allah the Glorified says: 
.And if it had been from any other than Allah, they would surely have found in it much discrepancy. (4:82)
(1) Ibn Talhah, Matalib, I, 141;
(2) al-Tabarsi, al-'Ihtijaj, I, 139;
(4) Narrated by Ibn Udhaynah from al-'Imam al-Sadiq (A) in al-Nuri, Mustadrak al-Wasa'il, III, 174; see also al-Saffar, Basa'ir al-darajat.