Whenever the Messenger of Allah ﷺ spoke, he would repeat his words three times so that they would be understood.
أن رسول الله ﷺ كان إذا تكلم تكلم ثلاثا لكي يفهم عنه.
No references are available.
Tabarani (8095) narrated it from Abu Habib Zayd bin Muhtadi Marwazi, who said, Ali bin Khashram narrated to us, Fadl bin Musa narrated to us, from Husayn bin Waqid, from Abu Ghalib, from Abu Umama, and he mentioned it.Haythami said, "Its isnad is hasan."I say, it is as he said, for Abu Ghalib, whose name was Hazwar, and it is also said Saeed bin Hazwar, is a disputed narrator. Abu Hatim and Nasai declared him daif, while Daraqutni and others declared him trustworthy. He is acceptable as a corroborating witness.