1065 – ʿAbd Allāh ibn ʿĀmir ibn Rabīʿah said: “I lived through the time of Abū Bakr, ʿUmar, and ʿUthmān—may Allah be pleased with them—and those who came after them, and I never saw them strike a slave for slander (qadhf) with more than forty lashes.” Related by Mālik and by al-Thawrī in his Jāmiʿ ⦗1⦘.

Hadith grading:
The hadith is authentic.
In Awjaz al-Masālik fī Sharḥ Muwaṭṭaʾ Mālik it is stated: Al-Bayhaqī recorded it through the chain of Yaḥyā ibn Bukayr, from Mālik, from Ibn Abī al-Zinād, and then said: Al-Thawrī narrated it from Abū al-Zinād, who reported from ʿAbd Allāh ibn ʿĀmir ibn Rabīʿah: “I lived to see Abū Bakr, ʿUmar, and ʿUthmān, and the caliphs who followed them, and I never saw them lash a slave for slander with more than forty strokes.”
Al-Bayhaqī also transmitted it through another route, and its isnād is sound.