When the Messenger of Allah ﷺ was with me after the afternoon prayer, he would pray those two units.
أخبرنا إسمعيل بن مسعود عن خالد بن الحارث عن شعبة عن أبي إسحق قال سمعت مسروقا والأسود قالا نشهد على
كان رسول الله ﷺ إذا كان عندي بعد العصر صلاهما
No references are available.
Bukhari transmitted it in the Book of Prayer Times, chapter on what may be prayed after Asr, etc, hadith no. 593, and Muslim in the Book of the Prayer of Travelers, chapter on identifying the two units of prayer that the Prophet ﷺ used to pray after Asr, hadith no. 835/301.See the previous hadith (505) narrated from Shubah with this chain. It also appears in Kubra, hadith no. 1555.