When the children of Israel had been freed from slavery in Egypt by the immolation of the paschal lamb, they went out through the desert so that they might come to the promised land, and they reached Mount Sinai. On the fiftieth day after the Passover, the Lord descended upon the mountain in fire, accompanied by the sound of a trumpet and thunder and lightning, and with a clear voice He laid out for them the ten commandments of the law. As a memorial of the law He had given, He established a sacrifice to Himself from the first-fruits of that year, to be celebrated annually on that day… It is obvious to all who read what the immolation of the paschal lamb and the escape from slavery in Egypt meant, for “Christ our Passover is sacrificed for us.” He is the true Lamb who has taken away the sins of the world, who has redeemed us from the slavery of sin at the price of His blood, and by the example of His resurrection has shown us the hope of life and everlasting liberty. The law was given on the fiftieth day after the slaying of the lamb, when the Lord descended upon the mountain in fire; likewise on the fiftieth day after the resurrection of our Redeemer, which is today, the grace of the Holy Spirit was given to the disciples as they were assembled in the upper room. Appearing visibly and externally as fire, He shed rays of the light of knowledge invisibly on their inmost thoughts and kindled in them the inextinguishable ardor of charity…
There, on Sinai, the crashing of the thunder and the blasts of the trumpet resounded in the midst of flames of fire and flashes of lightning. Here, in the upper room, along with the vision of tongues of fire there “came a sound from heaven as of a rushing mighty wind.” But although in both bestowals, namely of the law and of grace, a sound was heard outwardly, yet here by a more extensive miracle, when the sound was heard there was present the power of a heavenly gift, which would teach the hearts of the disciples inwardly without a sound. There, after all the legal decrees had been heard, the entire people answered with one voice, “All the words which the Lord hath said will we do.” Here, after the assembly of the Church, which was being born, had received the enlightenment of the Spirit, they spoke of the wonders of God in the languages of all countries.
– Bede the Venerable, Homilies on the Gospels II.17
Locus Communis 