For most of our history the Holy Wednesday night service was Matins/Orthros alone, which continues the Holy Week narrative. However, beginning a few hundred years ago in Greek and Antiochian 
churches, Matins began to be replaced by Holy Unction. The Anointing was used as part of the preparation for Pascha Communion. In those days the Holy Eucharist was received rarely, for many only at Pascha, and there was extensive preparation – strict fasting all week, Confession and Holy Unction. This is still true in some places.
However, today Communions are far more frequent, and Holy Unction is also used much more often for healing those who have serious illness, as it was originally intended. Still the Holy Wednesday Anointing remains popular, at least in “Byzantine” Orthodoxy. I know Greek churches especially are full to overflowing this evening. Liturgical scholars now recommend that we do both Matins and Anointing services tonight – which is a whole lot! I’ll comment chiefly about Matins.
Matins (Orthros) for Holy Wednesday evening
Please remember to read the Gospel passages before you read these articles. In what follows I paraphrase and omit much.
Matins Gospel: Luke 22:1-39
There is so much to cover in these next days that in the readings we “anticipate”, less we miss anything. So this evening it is already Holy Thursday evening.
Jesus and the disciples are in the upper room at the house of John Mark’s mother – perhaps the Mark who later wrote the Gospel. Imagine having the Mystical Supper, the risen Lord’s Pascha night appearance and the descent of the Holy Spirit in your house!
Matthew, Mark and Luke all say this was the Passover meal. John says it was the night before the Passover – a mystery which I think has never been resolved.
In Luke Jesus says: “I have earnestly desired to eat this Passover with you before I suffer….I shall not eat it again till it is fulfilled in the Kingdom of God… I will not drink the fruit of the vine again till the Kingdom of God comes.” A pall must have fallen over the meal which is usually a celebration. They knew what was coming, but they couldn’t accept it.
At the appointed time during the meal Jesus took the unleavened bread, and added the puzzling words “This is my Body given for you.” And at the end: “This is my Blood shed for you.”
What could this mean? Some Christians have given complex philosophical explanations. Orthodox have not. We have just accepted what Christ said. To quote Queen Elizabeth I of England (of all people!), “He took the bread and brake it, And what the word did make it, That I believe and take it.” Simple enough.
If we need more, here is my own non-philosophical approach, only for what it’s worth. Our bodies are
where we are; we act through our bodies. The eternal unseen Christ had taken on a human Body born of Mary where His followers could locate Him, be with Him. The next day that Body would die. He would rise again in that Body and then take it into Heaven, yet promising He would be “with you always to the end of the age”. So now this bread ” is my Body”; this is where you will find me, locate me, be with me “to the end of the age”. Blood gives power, strength for the human body. So “This is my Blood”, my power, my strength for you.
“This is my Body given for you…, my Blood shed for you.” In the Holy Eucharist Christ pours into us all He accomplished through His life-giving Passion, Death and Resurrection.
“Do this in remembrance of me”. The Greek is “in anamnesis/ανάμνηση” of me “. Our English translation, “in remembrance of me” is extremely inadequate. In today’s usage that sounds as if all we’re doing is bringing Him to mind. But “Anamnesis” in New Testament Greek means a literal re-calling, calling again. “Do this to call me back among you”. This is what we do at every Divine Liturgy: “Blessed is He who comes in the name of the Lord.”
The above is only my opinion, which has helped me. It is definitely not Church dogma.
Christians later, guided by Saint Paul, would emphasize that the Church also is the Body of Christ – that He meets us, comes to us, strengthens us in the holy People of God, on earth and on high. As indeed He does this in all things, if we only have eyes to see, for there is no place where Christ our God is not! But to see that clearly, first we need to recognize, focus on His presence in the Holy Eucharist. “If we don’t find Him somewhere, we won’t find Him anywhere” – and this is the place our Lord Jesus Christ specifically appointed for us to find Him.
Judas now goes out to betray Him. Jesus again tells His apostles how to lead the Church – not by lording it over others but by serving them, leading them, just as He the Lord of all is servant of all and will now lead our way through death into the Resurrection. He promises His Apostles that they will sit with Him at His table in His Kingdom on thrones judging the tribes of Israel. Tonight they will fail, but He looks beyond tonight. He knows they will again be faithful.
Simon Peter especially. Simon, Satan is out to get you. “No, Lord, I will go with you to prison and death”, which He did in Rome 35 years later. But not tonight. Peter, before dawn you will deny me three times – and discover how weak you are. (This is something we all need to discover.) Once I sent you all out with nothing, so you would learn to depend on God alone. But now you need provisions, a moneybag, a sword, “for now that which is written about me comes to its conclusion”. He speaks in symbols. The disciples don’t understand: “Look, we have two swords.” Jesus said: “It is enough.”
Enough swords? No. That night Peter will use a sword, and Jesus will forbid it: “He who lives by the sword will die by the sword”. Like 
all the others, they do not understand. So now He will show them. He leads them out to the Mount of Olives and into the Garden of Gethsemane.
And now, in the next three days, we will follow with Him, with them through the final crucial events of Holy Week.
Holy Unction
Let me admit that I don’t understand why this Holy Wednesday Anointing is so very popular in many churches, so meaningful to so many people. To me it seems a sort of intrusion into the Holy Week narrative. (If you can explain it, please Comment below.)
I wonder if perhaps that is why people find Holy Unction so meaningful at this point – now to heal our sin-sick souls and our inner eyes and foggy minds – so that with our hearts and souls and minds at peace, we may enter into the wonderful events of these next three days and truly live them with the Lord.
When we are not longer shut-in and can go back to church, I suggest that before you are anointed on Holy Wednesday night you pray something like this: “Lord, open my eyes, my ears, my heart, and enter into my soul. Focus my wandering mind. Let me truly walk with you fully alert through your Passion and Death and into your holy Resurrection.
Next Post: Holy Thursday Divine Liturgy of Saint Basil