When God informs us in His Book that the noblest among His...
When God informs us in His Book that the noblest among His human creatures are the most righteous and His Messenger commands us to honor the members of his house when we honor him we infer that they are the most righteous after the Prophet. Had they not been so they would not deserve such a unique honor and the Prophet would not have instructed us to honor them whenever we honor his name. To do otherwise would not be in accord with the Holy Qur'an.
Thus by commanding us to pray for them whenever we pray for him the Prophet was actually informing us of their high merit being the most obedient to God and His Messenger.
THE RECORD ATTESTS TO THEIR MERIT All Muslims agree that Ali the Prophet's cousin whom the Prophet "pothered" and his wife Fatimah (the Lady of Light) the dearest child of the Messenger and their two children Al-Hassan and Al-Hussein are from the chosen members of the House of Mohammad and that they are included in our prayers for him. The high qualifications of the chosen relatives of Mohammad is the main reason for the very unique honor bestowed upon them.
Imam Ali stood above all others after the Prophet. He was the strongest supporter of the Messenger of God. He never hesitated to give his life for the promotion of Islam. The readers of history can easily know that Imam Ali was the top defender of Islam and the most adherent to its rules. (6)The Holy Qur'an Chapter 111. Imam Ali's attitude towards personal power and prestige was unique.
Whenever he had to choose between adherence to his ideals and the pleasures of the earthly life he unhesitatingly chose the former. History testifies that he preferred to lose the leadership of the Muslim World rather than to accept a condition in which he did not believe. He was offered this leadership contingent on his pledge to follow the Book of God the instructions of the Messenger and the traditions of the first two Caliphs in the absence of the Quranic and the Messenger's instructions.
He replied: "(I shall follow the Book of God and the instructions of His Messenger; and in the absence of specific teachings of the two sources) I shall endeavor to the best of my knowledge and ability." (7) His knowledge was amazing in its depth and extensiveness.