The Three Hierarchs: Saints Basil the Great, Gregory the Theologian and John Chrysostom.
Each has his personal feast day in the month of January; Basil on the 1st, Gregory on the 25th and Chrysostom on the 27th. The common feast we celebrate today was instituted in the 11th century, in the time of the Emperor Alexius Comnenus. At one time there was a quarrel among the people about who was the greatest of three. Some gave Basil the pre-eminence for his purity and courage; others Gregory for the unfathomable depth and height of his theological mind; others still Chrysostom for the wonderful beauty of his speech and the clarity of his presentation of the Faith. So the first were called Basilians, the second Gregorians and the third Johannites. But, by the providence of God, this dispute was resolved to the benefit of the Church and the yet greater glory of the three saints. The Bishop of Euchaita, John (June 14th), had a vision in his sleep, in which each of these saints appeared to him in great glory and indescribable beauty, and then all three together. They then said to him: ‘We are one in God, as you see, and there is no dispute among us…neither is there among us a first or a second.’ The saints advised Bishop John to compile a common feast for them and to set aside for them a day of common commemoration. The quarrel was settled as indicated by the wonderful vision; January 30 being set aside for the common commemoration of the three hierarchs. The Greeks regard this feast not only as a church festival but as their greatest national and scholastic holiday.
– From The Prologue from Ochrid: Lives of the Saints and Homilies For Every Day In The Year- Part One: January, February, March by Saint Nikolai Velimirovich, Translated by Mother Maria, Birmingham, UK, Lazarica Press, 1985.