In the Roman tradition, oaths were sworn upon Iuppiter Lapis or the Jupiter Stone located in the Temple of Jupiter, Capitoline Hill. Iuppiter Lapis was held in the Roman tradition to be an Oath Stone, an aspect of Jupiter in his role as divine law-maker responsible for order and used principally for the investiture of the oathtaking of office.
According to Cyril Bailey, in "The Religion of Ancient Rome" (1907):
We have, for instance, the sacred stone (silex) which was preserved in the temple of Iuppiter on the Capitol, and was brought out to play a prominent part in the ceremony of treaty-making. The fetial, who on that occasion represented the Roman people, at the solemn moment of the oath-taking, struck the sacrificial pig with the silex, saying as he did so, 'Do thou, Diespiter, strike the Roman people as I strike this pig here to-day, and strike them the more, as thou art greater and stronger.' Here no doubt the underlying notion is not merely symbolical, but in origin the stone is itself the god, an idea which later religion expressed in the cult-title specially used in this connection, Iuppiter Lapis.
- Bailey, Cyril (1907). The Religion of Ancient Rome. London: Archibald Constable & Co. Ltd. p. 7. Retrieved 2015-08-18.