Plutarch, The Life of Cato the Younger 19

Cato used to be the first to reach the senate and the last to leave it; and often, while the other senators were slowly assembling, he would sit and read quietly, holding his toga in front of the book. 

He never left the city when the senate was in session. But afterwards, when Pompey and his friends saw that he could never be prevailed upon or forced from his position in any unjust measures which they had at heart, they would contrive to draw him away by sundry legal advocacies for friends, or arbitrations, or business matters. 

Accordingly, Cato quickly perceived their design and refused all such applications, and made it a rule to have no other business on hand while the senate was in session. 

For it was neither for the sake of reputation, nor to gain riches, nor accidentally and by chance, like some others, that he threw himself into the management of civic affairs, but he chose a public career as the proper task for a good man, and thought that he ought to be more attentive to the common interests than the bee to its honey. 

And so he was careful to have the affairs of the provinces and decrees and trials and the most important measures sent to him by his connections and friends in every place. 

At one time he opposed Clodius the demagogue, who was raising agitation and confusion as a prelude to great changes, and was calumniating to the people priests and priestesses, among whom Fabia, a sister of Cicero's wife Terentia, was in danger of conviction. 

But Cato put Clodius to such shame that he was forced to steal away from the city; and when Cicero thanked him, Cato told him he ought to be thankful to the city, since it was for her sake that all his public work was done.  

In consequence of this he was held in high repute, so that an orator, at a trial where the testimony of a single witness was introduced, told the jurors that it was not right to give heed to a single witness, not even if he were Cato; and many already, when speaking of matters that were strange and incredible, would say, as though using a proverb, "This is not to be believed, even though Cato says it." 

Again, when a corrupt and extravagant man was expatiating in the senate on frugality and self-restraint, Amnaeus sprang to his feet and said: "Who can endure it, my man, when you sup like Lucullus, build like Crassus, and yet harangue us like Cato?"​ 

And other men also who were degraded and licentious in their lives, but lofty and severe in their speech, were mockingly called Catos.​ 

IMAGE: Alexandre Jacovleff, Roman Senators (1911)