Al-Nufaylī said, “He passed away in 136 AH.”
Muhammad ibn al-Muthannā held that he died in 132 AH.
ʿAttāb ibn Bashīr—and al-Bukhārī as well—placed his death in 137.
Abū ʿUbayd and Shabāb said it was in 138 AH.

Aḥmad also remarked, “He is not strong; he spoke in support of irjāʾ.”
Yaḥyā al-Qaṭṭān said, “We used to avoid Khuṣayf.”
ʿUthmān ibn ʿAbd al-Raḥmān al-Ṭarāʾifī said, “I saw Khuṣayf wearing black garments; he was then overseeing the public treasury.”

I say: his hadiths rise to the rank of fair (ḥasan).

I read to ʿUmar ibn ʿAbd al-Munʿim—on the authority of Zayd ibn al-Ḥasan—who informed us: Abū Bakr al-Anṣārī; who informed us: Abū Muḥammad al-Jawharī; who informed us: ʿUmar ibn Muḥammad al-Zayyāt; Jaʿfar al-Firyābī narrated to us; Isḥāq ibn Rāhwayh narrated to us; ʿAttāb ibn Bashīr narrated to us, from Khuṣayf, from Abū ʿUbaydah, from his father, from the Messenger of Allah ﷺ:

“When you are uncertain in your prayer whether you have performed three or four [rakʿahs], and your stronger assumption is that you have completed four, perform two prostrations, then give the salām. If your stronger assumption is that you have prayed three, offer one [additional] rakʿah, then recite the tashahhud, then make the two prostrations of forgetfulness, and finally give the salām.” (1)

Were this narration sound, it would bring relief to those afflicted by obsessive misgivings in prayer.