Praise be to Allah.
This hadith was narrated by Abu’sh-Shaykh in al-‘Azamah (4/1489-1491). He said:
Abu’t-Tayyib Ahmad ibn Rawh told us: ‘Ali ibn ‘Amr told us, from Ibraaheem ibn Moosaa al-Bahraani, from Muqaatil, from ‘Ikrimah, from Ibn ‘Abbaas (may Allah be pleased with him) who said: The Messenger of Allah (blessings and peace of Allah be upon him) came to us when we were sitting in circles in the mosque, and the Messenger of Allah (blessings and peace of Allah be upon him) said: “What are you doing?” We said: We are thinking about the sun and how it rises and sets. He said: “You are doing well. Be like this, and think about what is created; do not think about the Creator…
The isnaad (chain of narration) of this isnaad is da‘eef (weak). Its isnaad includes ‘Ali ibn ‘Amr, of whom the commentators on the book said: Perhaps he is ‘Ali ibn ‘Amr ibn al-Haarith ibn Sahl ibn Abi Hubayrah.
Based on that, even though some of the scholars regarded him as trustworthy, they stated that he sometimes got confused and narrated some weird reports.
Adh-Dhahabi summed up his status in al-Kaashif (2/45) by saying:
He was regarded as trustworthy, but he narrated weird reports. End quote.
Al-Haafiz ibn Hajar summed up his status by saying:
He is honest but is sometimes confused.
End quote from Taqreeb at-Tahdheeb (p. 404).
With regard to the narrator Ibraaheem ibn Moosaa al-Bahraani, he is majhool (unknown); no one knows who he is.
Ibn al-Muhibb as-Saamit deemed this hadith to be mawdoo‘ (fabricated), in his book Sifaat Raab al-‘Aalameen (p. 409-410).
With regard to the sentence “think about what is created; do not think about the Creator”, this was narrated in a number of other hadiths; none of their isnaads is free of weakness..
Some of the scholars are of the view that (these hadiths) strengthen one another.
As-Sakhkhaawi (may Allah have mercy on him) said:
With regard to the hadith “think about everything but do not think about Allah”,
Its isnaads are weak, but when taken together, this gives them some strength, and the meaning is sound. In Saheeh Muslim, it is narrated from Abu Hurayrah in a marfoo‘ report: “People will keep on asking questions until someone will say, ‘Allaah created the universe, but who created Allah?’ Whoever encounters anything like that, let him say, ‘Aamantu Billah (I believe in Allah).”
End quote from al-Maqaasid al-Hasanah (p. 260-261).
Shaykh al-Albaani (may Allah have mercy on him) said:
In general, this hadith, when all its isnaads are taken into consideration, is hasan in my view.
End quote from as-Silsilah as-Saheehah (4/395-397).
For more information, please see the answer to question no. 260258.
And Allah knows best.