SHAFAQNA – The blessed existence of Lady Fatima Zahra (AS) is the proof of Allah (SWT). If the Prophet (PBUH) is the proof is not because he is a prophet, is due to him being infallible and if Imam is the proof is not because he is Imam, is due to him being infallible. If a person is infallible, his/her words, deeds and utterances are proof. Now, Imamate and prophethood is a higher position but validity of words is due to being infallible, meaning this complete human being is infallible.
Such a human being does not say anything unless by the order of God and his/her words, deeds and utterances become proof. If we have a narration from Lady Fatima Zahra (AS) without doubt, we will issue Fatwa according to it because an infallible does not say anything except the truth. You can see Imam Ali (AS) referred to the words of Lady Fatima Zahra (AS) for his reasoning (on some points) .
 Kashful Qammeh, Vol. 1, page 466.
Source: Part of speech by the Grand Ayatollah Javadi Amoli, Qom, (10 April 2013).