The Imams must necessarily be most learned and the best of all people. Should they not be so, giving preference to the inferior without any cogent reason would follow, which is absurd by all rational and traditional standards.
The excellence of our Imams is well known. Their superiority is clearer than daylight and surer than the day which has passed.
source : http://www.islamicecenter.com/e-library/logic_islamic_rules/logic_islamic_rules_makarem_subhani_03.html
