The Quran contains evidence for the status and purity of the Prophets. Where does it talk about the status and purity of the Shia Imams?
Allah (SWT) Has ordered us in Quran : O you who believe , Obey Allah and obey the Messenger and your divine leaders. Sura 4, verse 59.
'This verse is very clear that it is obligatory to obey Allah absolutely and always, and to obey the Messenger absolutely and always and the divine leaders absolutely and always. This means that all their orders are according to Allah and the Messenger Hesse it is obligatory to obey them as we are ordered to obey Allah and the Messenger. This means that these divine leaders are fully pure and never commit any sin otherwise if they possibly commit any sin then Allah will never Order us to obey a person who might commit a sin as such order can lead to commit a sin which is impossible.
'Sura 33, verse 33 is also clear that Ahlul Bayt are fully purified from any sin or error.
'With out the fact of the infallibility of Ahlul Bayt (Aas) it will be possible to follow any sinful act of the leaders. This is impossible to order Muslims to obey a sinner. Allah says in Quran: : My promised authority will never reach to sinners. Sura Baqara, verse 124, which is very clear that divine leaders can never be sinners.
Wassalam.