Mu’az ibn Jabal narrates that the Messenger of Allah (ص) said:
"Love for Ali is a good deed due to which sins bring no harm and enmity with him is a sin due to which good deeds bring no benefit"
Zamakhshari writes in explanation of such hadiths: This is because love for Ali is whole of faith and sins can do no harm to entire faith
Dailami, Ferdaus al-Akhbar, V.2, page 292; Qunduzi, Yanabi al-Muwadda, V.2, page 250, 292.