Peter, Archbishop of Alexandria

Reading from the Synaxarion:

Saint Peter illustriously occupied the throne of Alexandria for twelve
years, and, as Eusebius says, "was a divine example of a bishop on
account of the excellence of his life and his study of the sacred
Scriptures" (see Eusebius, Eccl. Hist., Book VII, 3 2; Book VIII 11, 13; and
Book IX, 6). He excommunicated Arius for his sympathy with the
Meletian schism. When Arius learned that Saint Peter had been imprisoned,
he sent many priests and deacons to him, asking that he receive him
back into the communion of the Church before his martyrdom. When the
ambassadors of Arius, who had not, like Saint Peter, perceived the ruin he
would engender, were astonished at the vehemence with which Saint Peter
refused to receive Arius again, he revealed to them a dread vision he had
seen, in which the Master Christ had appeared to him as a child wearing
a garment torn from head to foot. When Saint Peter asked the Lord
who rent His garment, the Lord answered that it was Arius, and that
he must not be received back into communion. The holy hieromartyr
Peter was beheaded during the reign of Maximinus in the year 312; he is
called the "Seal of the Martyrs," because he was the last Bishop of
Alexandria to suffer martyrdom under the pagan Emperors. His successors to
the throne of Alexandria, Saints Alexander and Athanasius the Great,
brought to final victory the battle against Arius' heresy which Saint
Peter had begun.

Kontakion in the Fourth Tone
O divine unshakeable towers of Christ's Church, pillars of true
piety who are most mighty and divine: Clement and Peter, ye
all-acclaimed, by your entreaties, protect and guard all of us.