All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad, sallallahu ‘alayhi wa sallam, is His slave and Messenger.
You are perhaps referring to the following hadeeth:
Jaabir ibn ʻAbdullah, may Allah be pleased with him, narrated, "I saw the Messenger of Allah, sallallahu ‘alayhi wa sallam, during his Hajj, on the Day of ʻArafah, while giving a sermon on his she-camel, Al-Qaswaa’. I heard him say, 'O people! Indeed, I have left among you that which if you hold fast unto it, you shall not go astray: the Book of Allah and my family, the people of my household.'" [At-Tirmithi]
If you are referring to this hadeeth, then you should know that it means that Muslims should follow the example of the members of his household and respect them as due.
Al-Munaawi commented on the hadeeth, saying, "It means that if you abide by the commands in the Quran, avoid what it forbade, and seek guidance in the biography of the members of his household, you shall be guided and will never be led astray. Al-Qurtubi said, 'This advice and this great emphasis entail the obligation of honoring, respecting, and loving his family as a confirmed religious obligation that no one has an excuse to neglect.'"
It should be noted, though, that the Muslim is enjoined to follow the example of the pious members of the Prophet's family who adhere to the Quran and Sunnah. Al-Munaawi also said: "Al-Hakeem (At-Tirmithi) said: What is meant by his family here are those who have (religious) knowledge and act upon it. They are the ones who do not part from the Quran. As for the ignorant or those with confused knowledge, they do not fit this description. The criterion here is the adherence to the Islamic virtues and avoidance of vices. A Muslim is enjoined to follow the useful knowledge even if it is imparted to him by other than the Prophet's family."
Allah knows best.