Every Orthodox Christian knows about the fasts for Pascha and Christmas. Some may know of the Dormition Fast, and even fewer follow it.
First, let's pause to reflect on the reason we fast. There is a misunderstanding that we should fast when we want something, as though the act of fasting somehow appeases God, and seeing us “suffer” gets Him to grant our request. Nothing can be further from the truth. It is not our fasting that pleases God, it is the fruits of our fast (provided we fast in the proper mindset, rather than treating it as a diet) that please Him.
We fast, not to get what we want, but to prepare ourselves to receive what God wants to give us.
Fasting turns us away from ourselves and toward God. In essence, it helps us become like the Theotokos, an obedient servant of God, who heard His word and kept it better than anyone else has or could.
So why do we fast before Dormition?
In a close-knit family, if the matriarch is on her deathbed, this would bring normal life to a standstill. Otherwise important things like parties, luxuries and personal desires, become unimportant. Life comes to revolve around the dying matriarch.
It is the same with the Orthodox family. The Church, through the Paraklesis Service, gives us the opportunity to come to that deathbed and eulogise and entreat the woman who bore God, the vessel of our salvation and our chief advocate at His divine throne.
Less time in leisure or other pursuits leaves more time for prayer and reflection on she who gave us Christ, and became the first and greatest Christian. Fasting, in its full sense (abstaining from food and other distracting desires) accomplishes this. In reflecting on the Theotokos and her incomparable life, we see a model Christian life, embodying Christ’s retort to the woman who stated that Mary was blessed because she bore Him: blessed rather are those who hear His word and keep it. Mary did this better than anyone. As Fr. Thomas Hopko has stated, she heard the word of God and kept it so well, that she of all women in history was chosen not only to hear His Word but give birth to it (Him).
So while we fast in contemplation of her life, we are simultaneously preparing ourselves to live a life in imitation of her. That is the purpose of the Dormition Fast.
The Fast of the Dormition lasts for two weeks, and begins on August 1 and ends on August 14, the day before the Feast of the Dormition.