There is a Hadith in Sahih Muslim:
Translation of Hadith: It has been narrated on the authority of Hadhrat Zaid bin Arqam (May Allah be well pleased with him) that one day, the Holy Prophet (Sallallahu alaihi wa sallam) gave a sermon at Ghadeer, which is between Makkah Mukarramah and Madina Munawwarah.
He (Sallallahu alaihi wa sallam) thanked Allah, praised Him and gave a sermon. He (Sallallahu alaihi wa sallam) advised us and reminded us of the next world (aakhirah) and then said:
“O People! Verily, I have come as a human being. Soon, a messenger from My Lord will come to me and I will accept his invitation. I leave behind, with you, 2 great ni'mah of Allah. One among them is the Book of Allah, in which there is "Hidayah" (Guidance) and "Noor" (Radiance). You accept the Book of Allah Ta’ala and hold on to it firmly. He (Sallallahu alaihi wa sallam) exhorted us towards the Holy Quran. Then said: The second ni'mah is My Ahle Bait; I remind you of Allah Ta’ala about My Ahle Bait; I remind you of Allah Ta’ala about My Ahle Bait….."
"I remind you of Allah Ta’ala about My Ahle Bait". The Holy Prophet (Sallallahu alaihi wa sallam) said this because love of Ahle Bait is for the love of the Holy Prophet (Sallallahu alaihi wa sallam) and love of the Holy Prophet (Sallallahu alaihi wa sallam) is for the love of Allah. Hence love of Ahle Bait will take you to Allah, so fear Allah Ta’ala about them in that no inappropriate word about them slips out from your tongue.
Hadhrat Mulla Ali Qari (May Allah Ta’ala shower His Mercy on him) writes in the interpretation of this Hadith: The Holy Prophet (Sallallahu alaihi wa sallam) said, I remind you of Allah Ta’ala about my Ahle Bait" times. The wisdom behind it is that the first time it meant His progeny and the second time, it meant the Ummahatul Momineen (May Allah Ta’ala be well pleased with them).