Let me put the explanation in a simple way:
THIS AUTHENTIC VERSION - Which mentions Quran as the only source holding which people will not go astray.
أَنَا تَارِكٌ فِيكُمْ ثَقَلَيْنِ أَوَّلُهُمَا كِتَابُ اللَّهِ فِيهِ الْهُدَى وَالنُّورُ فَخُذُوا بِكِتَابِ اللَّهِ وَاسْتَمْسِكُوا بِهِ ” . فَحَثَّ عَلَى كِتَابِ اللَّهِ وَرَغَّبَ فِيهِ ثُمَّ قَالَ ” وَأَهْلُ بَيْتِي أُذَكِّرُكُمُ اللَّهَ فِي أَهْلِ بَيْتِي
I am leaving among you two weighty things: the first one being the Book of Allah in IT there is right guidance and light, so hold fast to the Book of Allah and adhere to IT. He continued to encourage and urge regarding the Book of Allah. He then said: (secondly) and my AhlelBayt! I remind you of Allah with regard to the people of my household(Ahlelbayt). [Sahih Muslim #2408]
THIS ACTUAL VERSION WAS NARRATED IN THE BELOW FAULTY FORM.
أَنَا تَارِكٌ فِيكُمْ ثَقَلَيْنِ أَوَّلُهُمَا كِتَابُ اللَّهِ فِيهِ الْهُدَى وَالنُّورُ فَخُذُوا بِكِتَابِ اللَّهِ وَاسْتَمْسِكُوا بِهِ ” . فَحَثَّ عَلَى كِتَابِ اللَّهِ وَرَغَّبَ فِيهِ ثُمَّ قَالَ ” وَأَهْلُ بَيْتِي أُذَكِّرُكُمُ اللَّهَ فِي أَهْلِ بَيْتِي
I have left behind over you that which if you hold fast to IT you will never go astray: the Book of Allah – one end of IT is in the Hand of Allah and the other end of IT is in your hands– and my Ahl al-Bayt”.[Musnad Ishaq ibn Rahwayah].
Now my attempt was to explain the faulty version in the light of the Actual version. And how did the Actual version turn into the above one? Well That is because of the narrator who had weakness in narrating.
As simple as that.
I have addressed this, but will do so again collating everything I've said together clearly. I just want to point out again that the use of the singular {هِ/hi/hu= IT} has no relevance to our discussion. Why? If the narrator was , allegedly confused enough to believe the Ahlulbayt were included in what was left, after which we would never go astray, being a native Arab, as well as adding the Ahlulbayt in the Hadith, he would also have amended the grammar, being a native Arab fluent in his language. However, neither he, nor many, many others who narrate similar variants of this version have, but rather have used the singular {هِ/hi/hu= IT}, which demonstrates it is
perfectly acceptable in the Arabic language.
There are three key points i wish to make here:Point one:The tradition of Zayd b. Aqram occurred when he was very old and had forgotten much of what he remembered.
Even if he sincerely only tried to narrate what he felt he could remember, he still omitted authentic expressions.Indeed, every single version in Saheeh Muslim occurs when Zayd is very old and proclaims: "Zaid said, “By Allah! I have grown old and have almost spent up my age and I have forgotten some of the things which I remembered in connection with Messenger of Allah (saw), so accept what I narrate to you, do not compel me to narrate what I fail to narrate”.
In Ibn Majah with an authentic sanad we find him saying: "We said to Zaid bin Arqam: ‘Tell us a Hadith from the Messenger of Allah (saw).’ He said:
‘We have grown old and have forgotten, and (narrating) Ahadith from the Messenger of Allah (saw) is difficult (not a simple matter).’Those who suffer from memory loss may sincerely believe they are narrating what they remember, but are more likely to confuse and mix things up while thinking what they are saying is accurate. For sake of argument, let us not assume this necessarily, but accept he omitted authentic expressions, some of which even you agree with.
You agree, for example, and there is no difference between us, that another authentic expression is:
"They will never deviate until they meet me at the Hawdh (Pool of Kawthar at the highest level of Jannah"There is no dispute, and we are united in that this is an authentic expression, which Zayd has omitted here, perhaps due to forgetfulness.
Point two
The difference between the version of Zayd when he is old, and other versions are as follows:
In the Musnad of Ibn Rahwayh (teacher of Imam al-Bukhari) , as well as in the Mushkil al-Athar al-Tahawi, in a Hadith on the authority of Ali b. Abi Talib, that the Messenger of Allah (saw) had said:
“I have left behind over you (al-Thaqalayn), that which if you hold fast to it you will never go astray...the Quran...and my Ahlulbayt"
In Saheeh Muslim we find:
"I am leaving with you two weighty things: the first is the Book of Allah, in which there is right guidance and light, so hold fast to the Book of Allah and adhere to it...and my AhlulBayt...I remind you in the name of Allah of my Ahlulbayt ( three times)".
There is an authentic expression which is not in the Saheeh of Muslim, which does not contradict with it at all:
"If you hold fast to it you will never go astray"
Indeed, there is no contradiction between the two versions. They go in harmony, one placing in an authentic expression omitted by the other. Given the tradition has two Hasan chains, and many other Hasan chains due to the Shawahid, coming from many different chains of transmitters, it would be absurd to think they all united on the same error.
The only way you can dismiss the Hadith is if the tradition contradicts with the version of Saheeh Muslim. You can not use Dhann and speculation. I have to again emphasize, unless there is a contradiction, you can not throw away a Hasan hadith , with many, many chains and witnesses based on your own speculation of what could have happened.
So let us combine the traditions:
“I have left behind over you al-Thaqalayn, which if you hold fast to it you will never go astray, the Quran, , in which there is right guidance and light, so hold fast to the Book of Allah and adhere to it, and my Ahlulbayt. I remind you in the name of Allah of my Ahlulbayt ( three times).They will never deviate until they meet me at the Hawdh (Pool of Kawthar at the highest level of Jannah.Indeed, each of the three versions help to combine to give us a fuller picture and they go in harmony.
1. The Prophet (saw) begins by saying he is leaving behind the Thaqalayn, placing the Quran and Ahlulbayt side by side.
2. He proclaims that if we hold onto them, we will never go astray.
3. He emphasizes in the Quran there is guidance and light, so to hold onto it.
4. He then emphasizes his Ahlulbayt, which are of the two weighty things we hold onto to never go astray.
5. He beautifully emphasizes that the two go hand in hand by stating that they will never deviate from one another until they return to the Prophet (saw) at the highest level of Jannah.
How much clearer can the Messenger of Allah (saw) get? He uses many expressions to not only make it crystal clear, but to emphasize the Quran and the Ahlulbayt being side by side as sources of guidance. If this was a simple matter of asking the people to look after his family, why place the Quran side by side, why claim if we hold onto both we would never go astray, why emphasize the two will never deviate from each other until they reach the highest level of Jannah? This is hardly a call to give Khums to the Ahlulbayt, and many Sunni scholars have recognized it is a far greater command onto humanity.