I say: This chain is weak. Abū Harīz’s name was Abdullah ibn Husayn al-Basrī, the judge of Sijistān. Al-Dhahabī included him in al-Duafā and said: “Abū Dāwūd said, ‘His hadith is worthless.’ A number of scholars declared him weak, while Abū Zura deemed him trustworthy.” Al-Hāfiz said in al-Taqrīb: “Truthful, but prone to error.”
However, the hadith has a corroborating report from Abū Saīd that raises it to the level of acceptable. I documented it in Silsilat al-Ahādīth al-Daīfa (1463).
292—(He, peace be upon him, said: “Seek treatment, for the One who created disease also created its cure.” Al-Bukhārī.) p. 233
Authentic. Al-Bukhārī did not record it with this wording, nor did any of the other leading authorities whose works I consulted. They did, however, record many hadiths with the same meaning. The closest is the hadith of Anas, according to which the Messenger of Allah, peace and blessings be upon him, said: “When Allah, Mighty and Majestic, created disease, He also created its cure; therefore, seek treatment.” Ahmad recorded it in al-Musnad (156/3) through Harb, who said: I heard Imrān al-Ammī say: I heard Anas say—and he then cited it. This is a good chain. Its narrators are trustworthy and among those used by Muslim, with the exception of Imrān, who was Ibn Qudāma al-Ammī. Ibn Abī Hātim (303/1/3) quoted his father as saying: “There is nothing objectionable in his hadith, though he narrated only a few reports.”
Similar to it is the hadith of Abū Saīd al-Khudrī, traced back to the Prophet: “Allah has not sent down any disease—or has not created any disease—without also sending down or creating a cure for it. Those who know it know it, and those unaware of it remain unaware, except for al-sām.” They asked, “O Messenger of Allah, what is al-sām?” He replied: “Death.”
Al-Hākim recorded it (401/4) through Shabīb ibn Shayba, who said: Atā ibn Abī Rabāh narrated to us: Abū Saīd al-Khudrī narrated to us.
I say: This chain is acceptable for corroboration. All its narrators are trustworthy except this Shabīb, who was truthful but made errors in hadith, as al-Hāfiz stated in al-Taqrīb.