Before getting into the topic, a misconception first needs to be corrected. Many have mistaken this Hadeeth to be in Saheeh al-Bukhaari, this is not true at all. Imaam al-Bukhaari does not give a chain to this narration and he does not mention it as a saying of the Prophet. He merely put the wording as a topic heading. So no one can say this Hadeeth is a rawi of al-Bukhaari relating to Rasoolullaah.
Now to proceed…
From Sunan ibn Maajah:
حَدَّثَنَا نَصْرُ بْنُ عَلِيٍّ الْجَهْضَمِيُّ حَدَّثَنَا عَبْدُ اللَّهِ بْنُ دَاوُدَ عَنْ عَاصِمِ بْنِ رَجَاءِ بْنِ حَيْوَةَ عَنْ دَاوُدَ بْنِ جَمِيلٍ عَنْ كَثِيرِ بْنِ قَيْسٍ
Hadathanaa Nasr bin ‘Ali al-Jahdami, Hadathanaa ‘Abdullaah bin Daawood, ‘An ‘Aasim bin Rajaa’ bin Haywa, ‘An Daawood bin Jameel, ‘An Katheer bin Qays said:
“I was sitting with Abu Darda’ in the mosque of Damascus when a man came to him and said: ‘O Abu Darda’, I have come to you from al-Madinah, the city of Rasoolullaah, for a Hadeeth which I have heard that you narrate from the Prophet.’ He said: ‘Did you not come for trade?’ He said: ‘No.’ He said: ‘Did you not come for anything else?’ He said: ‘No.’ He said: ‘I heard Rasoolullaah say: “Whoever follows a path in the pursuit of knowledge, Allah will make easy for him a path to Paradise. The angels lower their wings in approval of the seeker of knowledge, and everyone in the heavens and on earth prays for forgiveness for the seeker of knowledge, even the fish in the sea. The superiority of the scholar over the worshiper is like the superiority of the moon above all other heavenly bodies. The scholars are the heirs of the Prophets, for the Prophets did not leave behind a Dinar or Dirham, rather they left behind knowledge, so whoever takes it has taken a great share.'”
‘Aasim bin Rajaa’ bin Haywa عَاصِمَ بْنَ رَجَاءِ بْنِ حَيْوَةَ
No man of Jarh wa Ta’deel considered him as Thiqah. He was declared weak by ad-Daaraqutni.
Daawood bin Jameel دَاوُدَ بْنِ جَمِيلٍ
He is unanimously declared as weak by all Imaams of Hadeeth. Ad-Daaraqutni considered him to be Da’eef Majhol.
Katheer bin Qays (or Qays bin Katheer) كَثِيرِ بْنِ قَيْسٍ
His real name is unknown. Some reported him to be Qays bin Katheer, while others reported his name as Katheer bin Qays. However, he was declared weak anyways by the likes of ad-Daarqutni and Mohammed bin Ibraaheem bin Sami’.
So we have three defects in a row, one after another, making this Hadeeth inauthentic without a doubt.
From Jaami’ at-Tirmidhi:
حَدَّثَنَا مَحْمُودُ بْنُ خِدَاشٍ الْبَغْدَادِيُّ، حَدَّثَنَا مُحَمَّدُ بْنُ يَزِيدَ الْوَاسِطِيُّ، حَدَّثَنَا عَاصِمُ بْنُ رَجَاءِ بْنِ حَيْوَةَ، عَنْ قَيْسِ بْنِ كَثِيرٍ…
Hadathanaa Mohammed bin Khidaash al-Baghdaadi, Hadathanaa Mohammed bin Yazeed al-Waasiti, Hadathanaa ‘Aasim bin Rajaai’ bin Haywa, ‘An Qays bin Katheer…
Both ‘Aasim and Qays bin Katheer (or Katheer bin Qays) appear in this isnaad. Their weakness has already been mentioned. Imaam at-Tirmidhi himself said the chain is disconnected.
From Sunan Abu Daawood:
…حَدَّثَنَا مُسَدَّدُ بْنُ مُسَرْهَدٍ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ دَاوُدَ، سَمِعْتُ عَاصِمَ بْنَ رَجَاءِ بْنِ حَيْوَةَ، يُحَدِّثُ عَنْ دَاوُدَ بْنِ جَمِيلٍ، عَنْ كَثِيرِ بْنِ قَيْسٍ
Hadathanaa Mosaddad bin Mosarhad, Hadathanaa ‘Abdullaah bin Daawood, Sami’to ‘Aasim bin Rajaai bin Haywa, Yohaddatha ‘An Daawood bin Jameel, ‘An Katheer bin Qays…
‘Aasim bin Rajaa, Daawood bin Jameel and Katheer bin Qays.
From Saheeh ibn Hibban:
أَخْبَرَنَا مُحَمَّدُ بنُ إِسْحَاقَ الثَّقَفِيُّ ، قَالَ : حَدَّثَنَا عَبْدُ الأَعْلَى بْنُ حَمَّادٍ ، قَالَ : حَدَّثَنَا عَبْدُ اللَّهِ بْنُ دَاوُدَ الْخُرَيْبِيُّ ، قَالَ : سَمِعْتُ عَاصِمَ بْنَ رَجَاءِ بْنِ حَيْوَةَ ، عَنْ دَاوُدَ بْنِ جَمِيلٍ ، عَنْ كَثِيرِ بْنِ قَيْسٍ
Akhbaranaa Mohammed bin IsHaaq ath-Thaqafi, Qaalaa Hadathanaa ‘Abd al-‘Ala bin Hammaad, Qaalaa Hadathanaa ‘Abdullaah bin Daawood al-Khoraybi, Qaalaa Sami’to ‘Aasim bin Rajaa’ bin Haywa, ‘An Daawood bin Jameel, ‘An Katheer bin Qays…
Once again, ‘Aasim bin Rajaa, Daawood bin Ibraheem and Katheer bin Qays appear in the isnaad, making it inauthentic.
We can safely conclude, without a doubt, this Hadeeth is inauthentic and not a saying of Rasoolullaah.