Rafida raised doubt against companion by saying:

in sahih muslim chapter of jumu’a-chapter of “fadhl” yawm al-jumu’a hadith number 854:
854 وحدثنا قتيبة بن سعيد حدثنا المغيرة يعني الحزامي عن أبي الزناد عن الأعرج عن أبي هريرة أن النبي صلى الله عليه وسلم قال خير يوم طلعت عليه الشمس يوم الجمعة فيه خلق آدم وفيه أدخل الجنة وفيه أخرج منها ولا تقوم الساعة إلا في يوم الجمعة
abu hurairah said : the prophet (saww) SAID : the best day in which the sun has risen is the Friday, in it Adam was created …etc
but in sahih abi khuzaimah abu hurarah said :
محمد بن يحيى ، حدثنا قال : نا محمد بن يوسف ، ثنا الأوزاعي ، عن يحيى ، عن أبي سلمة ، عن أبي هريرة : خير يوم طلعت فيه الشمس يوم الجمعة ، فيه خلق آدم ، وفيه أسكن الجنة ، وفيه أخرج منها ، وفيه تقوم الساعة ، قال : قلت له : أشيء سمعته من رسول الله صلى الله عليه وسلم ؟ قال : بل شيء حدثناه كعب

mohamed ibn yahya narrated mohamed ibn ussof narrated al-awza’i from yahya from abi salamah from abu hurairah he said : the best day in which the sun has risen is the Friday … so i asked him( abu salamah asking abu hurairah) : did you hear this from rasool allah ?? he ( abu hurairah) said :it’s rather something Kaab(Kaab al-ahbar ) told me !!!
here’s the hadith from sahih ibn khuzaimah :
محمد بن يحيى ، حدثنا قال : نا محمد بن يوسف ، ثنا الأوزاعي ، عن يحيى ، عن أبي سلمة ، عن أبي هريرة : خير يوم طلعت فيه الشمس يوم الجمعة ، فيه خلق آدم ، وفيه أسكن الجنة ، وفيه أخرج منها ، وفيه تقوم الساعة ، قال : قلت له : أشيء سمعته من رسول الله صلى الله عليه وسلم ؟ قال : بل شيء حدثناه كعب
so did abu hurairah hear this from the prophet or from Kaab and if it’s from kaab how could he attribute it to rasool allah (saww) ???
but more confusion is coming from the book of malik : muwatta malik :
243 وحدثني عن مالك عن يزيد بن عبد الله بن الهاد عن محمد بن إبراهيم بن الحارث التيمي عن أبي سلمة بن عبد الرحمن بن عوف عن أبي هريرة أنه قال خرجت إلى الطور فلقيت كعب الأحبار فجلست معه فحدثني عن التوراة وحدثته عن رسول الله صلى الله عليه وسلم فكان فيما حدثته أن قلت قال رسول الله صلى الله عليه وسلم خير يوم طلعت عليه الشمس يوم الجمعة فيه خلق آدم
narrated malik from yazeed ibn abdilleh ibn alhaad from mohamed ibn ibrahim ibn alharith altaimi from abi salamah ibn abdirrahman ibn awf that abu hurairah said : i went out… so i met Kaab Al-Ahbar so i sat with him and he told me about tawraat (Torah) and i told him about rasool allah , and amongst what i told him i said : the prophet (saww) said: the best day in which the son has risen is the The Friday …the hadith

Answered by brother Farid:

This deserves an explanation. First of all, let us collect the routes of the hadith in order to check which specific version was narrated by more narrators.
The narration from the Muwatta goes through Yazeed bin Abdullah bin Al-Had, through Mohammed bin Ibrahim bin Al-Harith Al-Taimi, through Abi Salama, to Abu Huraira. Abu Huraira is very specific in saying that he heard this hadith from the Prophet (sallalahu alaihi wa ala alihi wa sallam), and that Ka’ab checked the Torah to confirm this.

The second hadith is the hadith in Saheeh Muslim, from Harmala bin Yahya, though Ibn Wahb, through Yunus, through Ibn Shihab, through Abdulrahman Al-A’araj, through Abu Huraira who indicates that he heard this from the Prophet (sallalahu alaihi wa ala alihi wa sallam).

The third is also in Saheeh Muslim, through Qutaiba bin Sa’eed, through Al-Mugheera Al-Hizami, through Abi Al-Zinad, through Al-A’araj, up to Abu Huraira, to the Prophet (sallalahu alaihi wa ala alihi wa sallam).
A fourth can be found in Musnad Ahmad, through Yazeed, through Mohammed, through Abi Salama, through Abu Huraira, to the Prophet (sallalahu alaihi wa ala alihi wa sallam).
Another chain can also be found in Musnad Ahmad through Mohammed bin Mus’ab, through Al-Awza’ee, through Abi Ammar, through Abdullah bin Furookh, through Abu Huraira, to the Prophet (sallalahu alaihi wa ala alihi wa sallam).
Then again in Musnad Ahmad, through Yunus and Suraij, through Fulaih, through Sa’eed bin Al-Harith, through Abi Salama, that Abu Huraira narrated that the Prophet (sallalahu alaihi wa ala alihi wa sallam) narrated this hadith.
Al-Hakim narrated this through Abu Al-Abbas Mohammed bin Ya’qoub through Al-Rabee’ bin Sulaiman, through Abdullah bin Wahb, through Ibn Abi Al-Zinad, through his father, through Musa bin Abi Uthman, through his father, through Abu Huraira, to the Prophet (sallalahu alaihi wa ala alihi wa sallam). (Ibn Khuzaimah doesn’t include Abi Uthman though).

Notice the following:

The hadith is narrated by Abu Huraira through four of his students. They are the following:
Abi Salama – Al-A’araj – Abdullah bin Furookh – Abi Uthman
The following are the names of the students that narrated the hadith of each of their shaikhs up to Abi Huraira:
1- Abu Salama: Mohammed bin Ibrahim bin Al-Harith – Mohammed bin Amr bin Alqama – Sa’eed bin Al-Harith Al-Ansari
2- Al-A’araj: Ibn Shihab Al-Zuhri – Abu Al-Zinad
3- Abdullah bin Furookh: Abu Ammar
4- Abu Uthman: Musa bin Abi Uthman

So, here we have seven different chains up to Abu Huraira. Keep in mind that I am only limiting myself to what was quoted from the student of the student of Abu Huraira, since lists like this will never end. Plus, anything more is irrelevant. I also chose not to include a couple of other chains due to major weaknesses or due to them being disconnected.
As you have quoted, by Ibn Khuzaimah, the only chain that states that the hadith is that of Ka’ab Al-Ahbaar is that hadith of Yahya bin Abi Katheer through Abi Salama.
By this, he has went against seven other chains that state that this is the hadith of the Prophet (sallalahu alaihi wa ala alihi wa sallam), including three other students of Abi Salama that specifically reported that this is the hadith of the Prophet (sallalahu alaihi wa ala alihi wa sallam).
This was my initial view of this hadith, and I was reassured even further when I found Al-Albani’s commentary in Saheeh Ibn Khuzaimah. He said (p. 2/836):
الحديث كله صحيح مرفوعًا بلا ريب، ويكفي أن مسلمًا أخرجه من طريق الأعرج عن أبي هريرة، ورواه المصنف من طريقين آخرين عنه، فلعل العلة من يحيى فإنه مدلس.
Rough translation: The whole hadith is authentic without a doubt, and it is sufficient that (Imam) Muslim quoted it through Al-A’araj through Abi Huraira, and the author (Ibn Khuzaimah) narrated it through two other chains (Musa bin Abi Uthman and Abdullah bin Furookh), and it seems as through the issue is with Yahya bin Abi Katheer who is a mudalis.
I say: Al-Albani seems to be correct. The only chains that attribute this hadith to Ka’ab Al-Ahbaar are the chains with Yahya bin Abi Katheer. However, it isn’t necessary for one to believe that this is due to Yahya bin Abi Katheer making tadlees, but it simply being an error on his part is a major possibility.
This is an important statement that everyone should keep in mind about these hadiths:

Imam Muslim narrated in Kitab Al-Tamyeez (p. 95):
حدثنا عبد الله بن عبد الرحمن الدارمي حدثنا مروان الدمشقي عن الليث بن سعد حديثني بكير بن الأشج قال: قال لنا بسر بن سعيد: اتقوا الله، وتحفظوا من الحديث فوالله لقد رأيتنا نجالس أبي هريرة رضي الله عنه فيحدث عن رسول الله صلى الله عليه وسلم، ويحدثنا عن كعب، ثم يقوم فأسمع بعض من كان معنا – يجعل- حديث رسول الله صلى الله عليه وسلم عن كعب، وحديث كعب عن الرسول صلى الله عليه وسلم.
ٌٌٌRough translation: Busr bin Sa’eed said: Fear Allah and be cautious with hadith, by Allah we have sat with Abu Huraira and heard him narrated about the Prophet (sallalahu alaihi wa ala alihi wa sallam) and about Ka’ab Al-Ahbaar, then upon leaving, I hear those that are with us narrate the hadith of the Prophet (sallalahu alaihi wa ala alihi wa sallam) attributing it to Ka’ab, and the hadith of Ka’ab being attributed to the Prophet (sallalahu alaihi wa ala alihi wa sallam).

This is a very specific criticism by Busr, and it is really relevant when examining hadiths like the hadith quoted above.

It is due to this that we come to the conclusion that the errors here have nothing to do with Abu Huraira, since even his students are in agreement. However, it was only at the tabaqa of Yahya bin Abi Katheer that this issue arises.

Furthermore, it is worth mentioning that this hadith was narrated by other companions other than Abi Huraira.

A couple of notable examples are the hadiths of Abu Lubaba and Sa’ad bin Ubada, both can be found in Musnad Ahmad. Even though both of these hadiths are weak in theory, they do provide more evidence that the hadith is not by Ka’ab, but rather the words of the Prophet (pbuh).

Yet, a strong hadith does exist in Musnad Ahmad as well:
قال حدثنا حسين بن علي الجعفي عن عبد الرحمن بن يزيد بن جابر عن أبي الأشعث الصنعاني عن أوس بن أوس قال
قال رسول الله صلى الله عليه وسلم من أفضل أيامكم يوم الجمعة فيه خلق آدم وفيه قبض وفيه النفخة وفيه الصعقة فأكثروا علي من الصلاة فيه فإن صلاتكم معروضة علي فقالوا يا رسول الله وكيف تعرض عليك صلاتنا وقد أرمت يعني وقد بليت قال إن الله عز وجل حرم على الأرض أن تأكل أجساد الأنبياء صلوات الله عليهم
Rough translation: Hussain bin Ali Al-Ju’fi said: Abdulrahman bin Yazeed bin Jabir, through Abi Al-Ash’ath Al-San’aani, through Aws bin Aws, through the Prophet (pbuh) said, “The best of days are Fridays, it is when Adam was created, and died, and it is the time of the nafkh andsa’qa…”

Inshallah this is sufficient for the brothers that Abu Huraira has nothing to do with this, but rather, Yahya bin Abi Katheer. Especially if you are implying that his is attributing the hadiths of Ka’ab to the Prophet (pbuh) on purpose.