On this day, the eighth Sunday of Pascha, we celebrate Holy Pentecost.

Verses
In a mighty wind doth Christ distribute the Divine Spirit,
In the form of fiery tongues unto the Apostles.
In one great day, the Spirit was poured forth upon the Fishermen.

We celebrate this Feast of Holy Pentecost today in commemoration of the coming of the All-Holy Spirit into the world, which took place fifty days after the Resurrection of our Lord Jesus Christ from the dead.

Synaxarion

We have received this Feast from the Hebrew Bible; for, just as the Hebrews celebrate their own Pentecost, honouring the number seven, and because they received the Law fifty days after the Passover, so also do we, celebrating fifty days after Pascha, receive, instead of the Law, the All-Holy Spirit, Who gives us laws, guides us into all truth, and decrees what is pleasing to God.

It should be known that among the Hebrews there were three great Feasts: Passover, Pentecost, and Tabernacles. They observed Passover in commemoration of their deliverance from Egypt and their passage across the Red Sea; for “Pascha,” in the Hebrew language, means “passage.” This Feast signifies our own passage and return from the darkness of sin to Paradise.

They celebrated Pentecost in commemoration of the hardships they endured in the desert, where they received the Law, and of the way in which they were brought through many afflictions into the Promised Land, for then it was that they enjoyed fruit, wheat, and wine. It also signifies the hardship that we suffer from unbelief and our entry into the Church; for then it is that we partake of the Body and Blood of the Master.

The third Feast is that of Tabernacles, celebrated after the harvesting of fruits, that is, five months after the Feast of Passover. This Feast was celebrated in memory of the day on which Moses first pitched the Tabernacle that he saw on Mount Sinai in the cloud and which was constructed by the architect Beseleel. Fashioning tabernacles themselves, the Hebrews would celebrate the same Feast: living in the fields and giving thanks to God, they would reap the fruits of their labors. This Feast is a type of our resurrection from the dead, when, after our bodily tabernacles have been dissolved and reconstituted, we will enjoy the fruits of our labors, keeping festival in the eternal tabernacles.

It should be known that on this same day of Pentecost that we are celebrating, the Holy Spirit descended upon the Disciples. Since the Holy Fathers decided to divide up the Feast on account of the majesty of the All-Holy and Life-Creating Spirit, because He is One of the Holy and Life-Originating Trinity, we will speak tomorrow about the Descent of the Holy Spirit.

By the intercessions of Thy Holy Apostles, O Christ our God, have mercy on us. Amen.

Apolytikion in the Plagal of the Fourth Tone
Blessed are You, O Christ our God, who made fishermen all-wise, sending upon them the Holy Spirit and, through them, netting the world. O Loving One, glory to You.

Kontakion in the Plagal of the Fourth Tone
When the Most High came down and confused the tongues, He divided the nations; but when He distributed the tongues of fire He called all to unity. Therefore, with one voice, we glorify the All-Holy Spirit!

Source: https://www.johnsanidopoulos.com/2011/06/synaxarion-for-sunday-of-pentecost.html