The following is from Fr. Weber's English translation (with commentary) of the Roman Ritual (pre-Vatican II) "Blessing of a Bonfire", which is set in the books for the Vigil (yesterday) of the Feast of the Nativity St. John the Baptist (today). Your tradition may be different.
16. BLESSING OF A BONFIRE
on the Vigil of the Birthday of St. John the Baptist
conferred by the clergy outside of church
In the Church's veneration of her saints the cult of John the
Baptist had from earliest times and continues to have a most
prominent and honored place. John gave testimony of the true
light that shines in the darkness, although he proclaimed in
utter humility: "He must increase, but I must decrease." And the
Master also spoke in highest praise of His precursor: "I say to
you, among those born of women there is not a greater prophet
than John the Baptist." Attuned to the words of the Gospel the
Christians of former times were filled with love and enthusiasm
for this saint, and expressed a justifiable conviviality at the
approach of his feastday by lighting a bonfire the night before
in front of their churches, in the market-place, on the hilltops,
and in the valleys. The custom of St. John bonfires, indicative
of a people with unabashed and childlike faith, continues in some
places to this day.
P: Our help is in the name of the Lord.
All: Who made heaven and earth.
P: The Lord be with you.
All: May He also be with you.
Let us pray.
Lord God, almighty Father, the light that never fails and the
source of all light, sanctify + this new fire, and grant that
after the darkness of this life we may come unsullied to you who
are light eternal; through Christ our Lord.
The fire is sprinkled with holy water; after which the clergy and
the people sing the following hymn (for the music see the music
Hymn: Ut queant laxis
O for your spirit, holy John, to chasten
Lips sin-polluted, fettered tongues to loosen;
So by your children might your deeds of wonder
Meetly be chanted.
Lo! a swift herald, from the skies descending,
Bears to your father promise of your greatness;
How he shall name you, what your future story,
Scarcely believing message so transcendent,
Him for a season power of speech forsaketh,
Till, at your wondrous birth, again returneth,
Voice to the voiceless.
You, in your mother's womb all darkly cradled,
Knew your great Monarch, biding in His chamber,
Whence the two parents, through their offspring's merits,
Praise to the Father, to the Son begotten,
And to the Spirit, equal power possessing,
One God whose glory, through the lapse of ages,
P: There was a man sent from God.
All Whose name was John.
Let us pray.
God, who by reason of the birth of blessed John have made this
day praiseworthy, give your people the grace of spiritual joy,
and keep the hearts of your faithful fixed on the way that leads
to everlasting salvation; through Christ our Lord.