The Esala Poya or the Esala full moon day is in July according to the Gregorian calendar which is the one we use now. According to the Sinhala calendar this poya is in the month of Esala.
For Buddhists Esala Poya is very important as several important things happened on this day.
Prince Siddhartha was conceived in his mother’s, Queen Mahamaya Devi’s womb on an Esala full moon day.
The birth of Prince Siddhartha and Princess Yasodhara’s son, Prince Rahul also happened on an Esala Poya day.
It was on this very same day that Prince Siddhartha gave up his lay life and became an ascetic. He then went in search of Enlightenment or Buddhahood. But before he left the palace and lay life he went and looked at his son Prince Rahula and his wife Princess Yasodhara.
They were both fast asleep and therefore, did not see him.
What made Prince Siddhartha leave a life of luxury and become an ascetic? He saw an old man, a sick man and a dead man and realised that lay life was full of sorrow and that even he, a prince would become old, sick and would eventually die. Thus, he became disillusioned with lay life. The last person he saw on his journey through the city was a Sadhu.
Thus, Prince Siddhartha too wanted to become a Sadhu or ascetic and go in search of the truth which would end life’s sorrows
Prince Siddhartha’s leaving of the lay life is known as the 'Great Renunciation'. The Prince left the palace on his horse Kantaka accompanied by his Minister Channa. When they reached the banks of the river Neranjana, the prince removed his royal robes and donned the robes of an ascetic.
He gave his royal robes to Channa and told him to go back to the palace with the news of his 'Great Renunciation'. The weeping minister did as he was bade. The horse Kantaka died of a broken heart.
It is also on an Esala Poya Day that the Buddha preached his first sermon,the Dhammachakkapavattana Sutta to five ascetics known as the Pasvaga Mahanun. This was at a Deer Park in Isipatana in India. Isipatana is now known as Saranath. The five ascetics were, Kondanna, Bhaddiya, Vappa, Mahanama and Assaji. After they listened to the Sutta they became Buddhists and were the first bhikkhus in the Buddha Sasana.
In Sri Lanka too several important events took place on Esala Poya and, therefore, the Esala Poya is very important to Sri Lankan Buddhists.
It was Prince Ariththa, King Devanampiyatissa’s nephew who was ordained as the island’s first bhikkhu by Arahath Mahinda.
It was on an Esala Poya day that the laying of the foundation for the Ruwanvelisaya took place. The enshrinement of relics was done by King Dutugemunu.
It was on an Esala Poya Day that the Sacred Tooth Relic was brought to Sri Lanka by Princess Hemamala and Prince Dantha from India. The original home of the Sacred Tooth Relic was Danta Pura, (City of the Tooth) in the state of Kalinga, on the Eastern coastal belt of India (present Orissa). Princess Hemamala disguised herself as an ordinary woman and hid the Sacred Tooth Relic in her hair. The Royal couple landed at Lankapattana. walked to Anuradhpura and handed over the Sacred Tooth Relic to King Kithsirimevan (AD 303-331). The reason the Sacred Tooth Relic was sent to Sri Lanka was for protection.
The Sacred Tooth Relic was finally deposited in a building called Dhamma Cakka Geha built by King Devanampiyatissa.
The Sacred Tooth Relic was taken in a grand procession and kept there for three months.
This procession could be the origin of today’s annual Esala Dalada Perahera held in Kandy and associated with the Dalada Maligawa.