The new fire is one of the oldest Christian traditions and has its roots in the Old Testament practices of the Jews.
The early Christians continued the Jewish practice of lighting lamps in the evening, at the end of the Sabbath, but as a well-established Saturday night ritual, they used it to start their Sunday observances on Saturday night. This became the basis of the Lucernarium, a vigil rite that consisted of scripture readings and psalms, followed by Holy Mass. This was associated with a number of feast days, and possibly even every Sunday in some places, according to selected scholars.
Eusebius tells us that these lights became associated with the Easter Vigil as early as the third century, and also says that in the fourth century, Constantine set lamps throughout the city in observance of the Easter Vigil. St. Gregory of Nyssa suggests a similar practice in Cappdocia at the same time, and there are reports of Milan following suit. Like so many wonderful symbols of the Easter Vigil that tie the Old and New Testaments together, the fire was simultaneously an image of the pillar of fire that had led the Hebrews out of Egypt and also the light of the Paschal Lamb emerging from the darkened tomb during the night. The use of the new fire was not universal, as some bishops forbade them because they resembled the bonfires lit by pagans as part of their spring solstice celebrations. As ancient paganism died out, so did objections to the new fires.
From this the paschal candle arose as a singular symbol of the resplendent light emerging on Easter morning. Light was needed by which to proclaim the sacred scriptures and sing the paschal praises, and thus the light of the fire developed into the paschal candle, which carried the light into the church and among the faithful, and then functioned as the light by which the Exsultet, prophecies and gospel were proclaimed.
The large size of the paschal candle later developed into yet another custom, that of carrying several flames away from the new fire, lest the single flame of the paschal candle be blown out or lost while being carried into the church. This caused the creation of the triple-flamed reed, which was lit from the new fire and carried into the church, then used to light the paschal candle once inside. The reforms of the 1950’s did away with the reed and restored the paschal candle as being directly lighted from the new fire.