Orthodox perspective:
In one Father (we believe), the beginning, and cause of all:
begotten of no one, proceedeth of no one: without cause or generation,
alone subsisting: creator of all: but Father of one only by nature,
His Only-begotten Son and our Lord and God and Saviour Jesus Christ,
and proceedethor of the most Holy Spirit. (saint John of Damascus)
We understand Only-begotten as not created. When we read
In the beginning was the Word, and the Word was with God, and the Word
was God. (John 1,1)
we understand how the most Holy Spirit teaches us through the fathers of the church, that
the Word already existed when the first creation was made. This first creation is the time ("in the begining"). When time was created, the Word of God, which is the Son, participated Himself
He was with God in the beginning. (John 1,2)
Entire creation was made through the Son of God
Through him all things were made; without him nothing was made that
has been made. (John 1,3)
When we say "The Father, the Son, and the Holy Spirit", we not talk about three gods, but only one. Likewise, when we discuss about the sun and the sunshine (born from the sun), and the heat (proceedething from sun through the sunshine), we not talk about 3 suns, but only one. (saints Cyril and Methodius, explaining Trinity to saracens)
"The Father, the Son, and the Holy Spirit is one God" because Son is not separated from Father, and Father and Son are not separated from Holy Spirit
I am in the Father, and that the Father is in me (John 14:10)
When the Counselor comes, whom I will send to you from the Father, the
Spirit of truth who goes out from the Father, he will testify about me (John 15:26)
The Holy Spirit is not son of God, but He proceedeth from Father. In similar way, how Eva is not born from Adam like Set, but Eva is taken from Adam. (saint Gregory the Theologian)
As long as muslims accept that Christ is the Word of God and in the same time as a creation of the God, results that God is without word and without spirit, and mutilate Him. (saint John of Damascus)
When we read:
My Father, who has given them to me, is greater than all; no one can
snatch them out of my Father’s hand. (John 10:29)
we don't understand that Father is greater than Son, because the reason is written in the next verse:
I and the Father are one (John 10:30)
which means that Father is greater than all others, while Son is not inside "all others" since He is not separated by Father.
the only begotten Son, which is in the bosom of the Father (John 1:18)
From here we conclude also that the Son of God is greater than all, and the Holy Spirit is greater than all.
When we read
You heard me say, 'I am going away and I am coming back to you.' If
you loved me, you would be glad that I am going to the Father, for the
Father is greater than I. (John 14:28)
we do not understand any precedence in time or superiority in nature of the Father over the Son (for through His agency He made the ages), or superiority in any other respect save causation. And we mean by this, that the Son is begotten of the Father and not the Father of the Son, and that the Father naturally is the cause of the Son just as we say in the same way not that fire proceedeth from light, but rather light from fire. So then, whenever we hear it said that the Father is the origin of the Son and greater than the Son, we understand it to mean in respect of causation. (saint John of Damascus)
When we read:
But if I drive out demons by the Spirit of God, then the kingdom of
God has come upon you. (Matthew 12:28)
we deduce that to cast out devils is a work of the greatest power, and not of any ordinary grace. And He means indeed that from these things we infer and say, If this be so (and it is), then the Son of God has come (saint John Chrysostom)
When we read:
About three in the afternoon Jesus cried out in a loud voice, “Eli,
Eli,[a] lema sabachthani?” (which means “My God, my God, why have you
forsaken me?”) (Matthew 27:46)
we not understand that He felt these sufferings departed from God, or the divine nature abandoned the human nature on the Cross in order for Christ to feel the pain, the suffering from this abandonment. We understand how father John Chrysostom (temple and mouth of Holy Spirit) says:
... after this He speaks, that they might learn
that He was still alive, and that He Himself did this, and that they
might become by this also more gentle, and He says, Eli, Eli, lama
sabachthani? Matthew 27:46 that unto His last breath they might see
that He honors His Father, and is no adversary of God. Wherefore also
He uttered a certain cry from the prophet, even to His last hour
bearing witness to the Old Testament, and not simply a cry from the
prophet, but also in Hebrew, so as to be plain and intelligible to
them, and by all things He shows how He is of one mind with Him that
begot Him.
Because the rabbi told before:
He trusts in God. Let God rescue him now if he wants him, for he said,
'I am the Son of God.' (Matthew 27:43)
The Hebrew words of the Lord on the Cross, were supposed to remember about fulfiling the profetic words from David's psalm 22, which depicts His passion, crucifixion and triumph:
1 My God, my God, why hast thou forsaken me? why art thou so far from
helping me, and from the words of my roaring?
2 O my God, I cry in
the daytime, but thou hearest not; and in the night season, and am not
silent.
3 But thou art holy, O thou that inhabitest the praises of
Israel.
4 Our fathers trusted in thee: they trusted, and thou
didst deliver them.
5 They cried unto thee, and were delivered:
they trusted in thee, and were not confounded.
6 But I am a worm,
and no man; a reproach of men, and despised of the people.
7 All
they that see me laugh me to scorn: they shoot out the lip, they shake
the head, saying,
8 He trusted on the LORD that he would deliver
him: let him deliver him, seeing he delighted in him.
9 But thou
art he that took me out of the womb: thou didst make me hope when I
was upon my mother's breasts.
10 I was cast upon thee from the
womb: thou art my God from my mother's belly.
11 Be not far from
me; for trouble is near; for there is none to help.
12 Many bulls
have compassed me: strong bulls of Bashan have beset me round.
13
They gaped upon me with their mouths, as a ravening and a roaring
lion.
14 I am poured out like water, and all my bones are out of
joint: my heart is like wax; it is melted in the midst of my bowels.
15 My strength is dried up like a potsherd; and my tongue cleaveth
to my jaws; and thou hast brought me into the dust of death.
16
For dogs have compassed me: the assembly of the wicked have inclosed
me: they pierced my hands and my feet.
17 I may tell all my bones:
they look and stare upon me.
18 They part my garments among them,
and cast lots upon my vesture.
19 But be not thou far from me, O
LORD: O my strength, haste thee to help me.
20 Deliver my soul
from the sword; my darling from the power of the dog.
21 Save me
from the lion's mouth: for thou hast heard me from the horns of the
unicorns.
22 I will declare thy name unto my brethren: in the
midst of the congregation will I praise thee.
23 Ye that fear the
LORD, praise him; all ye the seed of Jacob, glorify him; and fear him,
all ye the seed of Israel.
24 For he hath not despised nor
abhorred the affliction of the afflicted; neither hath he hid his face
from him; but when he cried unto him, he heard.
25 My praise shall
be of thee in the great congregation: I will pay my vows before them
that fear him.
26 The meek shall eat and be satisfied: they shall
praise the LORD that seek him: your heart shall live for ever.
27
All the ends of the world shall remember and turn unto the LORD: and
all the kindreds of the nations shall worship before thee.
28 For
the kingdom is the LORD'S: and he is the governor among the nations.
29 All they that be fat upon earth shall eat and worship: all they
that go down to the dust shall bow before him: and none can keep alive
his own soul.
30 A seed shall serve him; it shall be accounted to
the Lord for a generation.
31 They shall come, and shall declare
his righteousness unto a people that shall be born, that he hath done
this.
This cry of Christ, says that Christ was not abandoned either by His Father or by His own divinity, as if fearing the Passion and shrinking from the suffering of Christ. So what happened? By this cry Christ "stamps on Himself what is ours". In other words, at that moment Christ is speaking in our place. For we were those abandoned and overlooked and then assumed and saved by the Passion of the impassible One. (saint Gregory the Theologian)
Orthodoxy, by its tradition, conserves everything that God revealed to humanity in all times, through all His saints.