To publish the Gospel law, he renewed these four things, but in a much more excellent way. The work began with a great noise: but it was neither the violence of thunder, nor the sound of trumpets, as we hear in a fight; the noise which God sent was like that of an impetuous wind, which represented the Holy Spirit; and who, without being terrible or threatening, filled the whole house, and called all of Jerusalem to the beautiful spectacle which God was going to give them. We saw a fire, but pure and smoke-free, which did not appear from afar to frighten the disciples, but whose innocent flame, without burning them or singeing their hair, rested on their heads. This fire penetrated inside, and by this means the law of the Gospel was gently imprinted, not in insensible stones, but in a heart composed of flesh, and softened by grace. There was a word, which multiplied admirably. In place on Mount Sinai God spoke one language, and one people; in the evangelical publication which was to bring together in one all the peoples of the universe in the faith of Jesus Christ and the knowledge of God, in a single speech we heard all languages, and each people heard their own. So Jesus established his law much differently than Moses. Let us believe, hope, love, and the law will be in our hearts. Let us prepare inner ears for him, simple attention, a gentle fear which ends in love.
From above Mount Sinai God cried out: Do not come near me, either men nor animals; life is at stake; and everything that approaches will die of death. On the holy mountain of Zion, God does not only approach the figure with a luminous flame, but he enters inside the heart: this beautiful fire takes the form of a tongue; the Holy Spirit comes to speak to the hearts of the Apostles; and from their hearts must come out the word which will convert the whole universe.
It’s worth noting that the feast of Pentecost, originally the Jewish feast of first fruits, was a celebration of the giving of the Law. I’m not sure whether Bossuet was aware of this (it wouldn’t surprise me if he was) but he certainly puts the two together.