Suetonius Caligula 5

At the time of his death, however, and afterwards, they displayed still greater and stronger proofs of their extraordinary attachment to him. The day on which he died, stones were thrown at the temples, the altars of the gods demolished, the household gods, in some cases, thrown into the streets, and new-born infants exposed. It is even said that barbarous nations, both those engaged in intestine wars, and those in hostilities against us, all agreed to a cessation of arms, as if they had been mourning for some very near and common friend; that some petty kings shaved their beards and their wives heads, in token of their extreme sorrow; and that the king of kings ¹ forbore his exercise of hunting and feasting with; his nobles, which, amongst the Parthians, is equivalent to a cessation of all business in a time of public mourning with us.