The ancients considered the Numa tradition to be the oldest, purest, and most reverent form of the cultus of the Romans. Numa Pompilius, a Sabine by birth and second king of Rome, received this tradition from the Gods, through Egeria in the sacred grove of Carmentis, and through direct contact with the highest gods. He is said to have established a religious calendar of feast days, the rites to be performed, and the various priesthoods of flamines, Vestales Virgines, the Salii, augures, and pontifices.
In times of great distress the City of Rome would renew itself by returning to the Numa tradition. The first time came with the expulsion of the kings and establishment of the Republic around 509 BCE. The second time followed the Gallic sack of Rome in 390 BCE. Following the Civil Wars in the Late Republic, some Romans once again advocated a return to the Numa tradition as a way to restore Rome.
The Numa tradition was generally regarded to have forbidden the use of blood sacrifices. Ovid tells an amusing story of Numa meeting with highest Jupiter, where Jupiter demands a sacrifice and Numa plays with him, getting Jupiter to agree instead to a sacrifice of chopped leeks, the hair of a man, and fish  . A variation of the story is told by Plutarch in the "Life of Numa". Speaking of the rituals handed down from Numa Pompilius, Plutarch wrote, "they were not celebrated with effusion of blood, but consisted of flour, wine, and the least costly offerings." Blood sacrifices were supposedly introduced when Ceres demanded the sacrifice of a pig  . This could possibly refer to the time when a new cultus was introduced for Ceres with the erection of a temple for her, Liber, and Libera on the Aventine Hill around 494 BCE. Such legends are much later in origin, probably from the fourth century, but in the late Republic there was the idea of a Numa tradition in the early religio Romana when simple offerings provided a much more reverent worship of the Gods. Those traditions relate back to Carmentis and the cultus that was devoted to her in her sacred grove. Only later were immolationes introduced.
"Formerly what served to reconcile Gods and men was spelt and pure salt's glistening grain. ... A man was wealthy if he could add violets to crowns fashioned from meadow flowers; the knife which eviscerates a pole-axed bull had no role in the sacred rites. Ceres first delighted in a greedy sow's blood" (Ovid Fasti 1.337-49).
"The Gods," said Varro, "do not desire blood sacrifice; their images even less."
- "The Gods are not to be represented in the form of man or beast, nor are there to be any painted or graven image of a deity admitted (to your rites)."
- "When you sacrifice to the celestial Gods, let it be with an odd number; when to the terrestrial, with even."
- "Sacrifices are not to be celebrated with an effusion of blood, but consist of flour, wine, and the least costly of offerings."
- "No sacrifices shall be performed without meal (mola salsa)."
- "You shall not stir the fire with a sword."
- "You shall not make to the Gods libation of wine from an unpruned vine."
- "Do not sprinkle wine on a funeral pyre."
- "Turn round to pay adoration to the gods; sit after you have worshipped."
- "When you go out upon a journey, look not behind thee."
Romulus, the first king of Rome, had dedicated the first Roman sanctury of the City (Livy, I.10.5-7). This was an oak tree on the Capitoline Hill where the spoils of war were to be offered to Jupiter Feretrius. Later, Numa Pompilius then provided a lex templi for this Romulan shrine:
"The man under whose auspices the opima spolia are won in full battle should dedicate them to Jupiter Feretrius; he should sacrifice an ox; let him who took them [give three] hundred in bronze. For the second spoils, let him sacrifice solitaurilia, whichever he wishes, at the altar of Mars in the Campus Martius. For the third spoils, let him sacrifice to Ianus Quirinus a male lamb; let him who took them give one hundred in bronze. Let the man under whose auspices they were taken make any necessary piacular offering to the Gods."