Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him) said:
“No one among the respectable Muslim scholars has said that ‘Ali was more knowledgeable or had more understanding of Islam than Abu Bakr and ‘Umar, or even than Abu Bakr alone. Those who claim that there is consensus on that are among the most ignorant of people and the greatest liars. Rather, more than one of the scholars have stated that there is scholarly consensus that Abu Bakr al-Siddeeq was more knowledgeable than ‘Ali, such as Imam Mansoor ibn ‘Abd al-Jabbaar al-Sam’aani al-Marwadhi, one of the leading scholars of the Sunnah among the companions of al-Shaafa’i, who mentioned in his book Taqweem al-Adillah ‘ala’l-Imam that there was consensus among the scholars of the Sunnah that Abu Bakr was more knowledgeable than ‘Ali. I do not know of anyone among the famous imams who disputes this point. How could it be otherwise when Abu Bakr al-Siddeeq used to issue rulings and commands and prohibitions, and pass judgements, and deliver khutbahs in the presence of the Prophet (peace and blessings of Allaah be upon him), as he used to do when he and Abu Bakr would go out to call the people to Islam, and when they migrated together, and on the day of Hunayn, and on other occasions, when the Prophet (peace and blessings of Allaah be upon him) remained silent and approved of what Abu Bakr said; no one else enjoyed such status. When the Prophet (peace and blessings of Allaah be upon him) consulted with the wise and knowledgeable men among his companions, he would consult Abu Bakr and ‘Umar first, because they were the first to speak about matters of Islam in the presence of the Messenger (peace and blessings of Allaah be upon him) before the rest of his companions; for example when he consulted them about the prisoners of Badr, the first ones who spoke about that were Abu Bakr and ‘Umar, and this also happened on other occasions… In Saheeh Muslim it is narrated that the companions of the Prophet (peace and blessings of Allaah be upon him) were with him on a journey and he said: “If the people obey Abu Bakr and ‘Umar, they will be guided aright.” And it was narrated from Ibn ‘Abbaas that he used to give his fatwas based on the Book of Allaah, and if he could not find anything then he would look at the Sunnah of the Messenger of Allaah (peace and blessings of Allaah be upon him), then if he could not find anything he would refer to the fatwas of Abu Bakr and ‘Umar, then if he did not find anything he would refer to the fatwas of ‘Uthmaan and ‘Ali – and Ibn ‘Abbaas was the habr al-ummah (scholar of the ummah) and the most knowledgeable of the Sahaabah of his time, and he would consult the words of Abu Bakr and ‘Umar and give them precedence over the words of anyone else among the Sahaabah. And it was proven that the Prophet (peace and blessings of Allaah be upon him) prayed for Ibn ‘Abbaas and said, “O Allaah, cause him to understand the religion of Islam and teach him the correct interpretation (of the Qur’aan).”
Majmoo’ al-Fataawa, 4/398