The Pledge

Every book on the Pony Express, without exception, has quoted the oath that [Alexander] Majors made his employees take. This one is no different.

It should probably be mentioned—though it rarely is—that the oath was originally meant for men on the ox trains, and while there is evidence that Pony riders did take it, it's not like records were kept indicating that every single rider, let alone every employee, did. And there's plenty of testimony from Richard Burton, and others, that at least some of the provisions—cussing most prominently—were more observed in the breach.

It's somewhat picturesque to imagine someone like Jack Slade taking the oath; you can almost see him spitting a wad of tobacco out between phrases and toasting the conclusion with a bottle of Julesburg's best. But it's an integral part of Pony lore, and there were plenty of Pony riders who took it seriously:

I ________, do hereby swear, before the great and Living God, that during my engagement, and while I am an employee of Russel, Majors & Waddell, I will, under no circumstances, use profane language; that I will drink no intoxicating liquors; that I will not quarrel or fight with any other employee of the firm, and that in every respect I will conduct myself honestly, be faithful to my duties, and so direct all my acts as to win the confidence of my employers. So help me God.

Source: West Like Lightning The Brief, Legendary Ride of the Pony Express (2018) by Jim DeFelice.