Originally the verses in the Scripture weren’t numbered as they are now so when someone wanted to point to a passage he didn’t give the verse numbers but simply quoted the begging of the passage. That’s what Jesus is doing on the Cross. As those before said, he is referring to Psalm 22 which says:
1 My God, my God, why have you forsaken me?
Why are you so far from saving me,
so far from the words of my groaning?
2 O my God, I cry out by day, but you do not answer,
by night, and am not silent.
3 Yet you are enthroned as the Holy One;
you are the praise of Israel.
4 In you our fathers put their trust;
they trusted and you delivered them.
5 They cried to you and were saved;
in you they trusted and were not disappointed.
6 But I am a worm and not a man,
scorned by men and despised by the people.
7 All who see me mock me;
they hurl insults, shaking their heads:
8 “He trusts in the LORD;
let the LORD rescue him.
Let him deliver him,
since he delights in him.”
9 Yet you brought me out of the womb;
you made me trust in you
even at my mother’s breast.
10 From birth I was cast upon you;
from my mother’s womb you have been my God.
11 Do not be far from me,
for trouble is near
and there is no one to help.
12 Many bulls surround me;
strong bulls of Bashan encircle me.
13 Roaring lions tearing their prey
open their mouths wide against me.
14 I am poured out like water,
and all my bones are out of joint.
My heart has turned to wax;
it has melted away within me.
15 My strength is dried up like a potsherd,
and my tongue sticks to the roof of my mouth;
you lay me in the dust of death.
16 Dogs have surrounded me;
a band of evil men has encircled me,
they have pierced my hands and my feet.
17 I can count all my bones;
people stare and gloat over me.
18 They divide my garments among them
and cast lots for my clothing.
19 But you, O LORD, be not far off;
O my Strength, come quickly to help me.
20 Deliver my life from the sword,
my precious life from the power of the dogs.
21 Rescue me from the mouth of the lions;
save me from the horns of the wild oxen.
22 I will declare your name to my brothers;
in the congregation I will praise you.
23 You who fear the LORD, praise him!
All you descendants of Jacob, honor him!
Revere him, all you descendants of Israel!
24 For he has not despised or disdained
the suffering of the afflicted one;
he has not hidden his face from him
but has listened to his cry for help.
25 From you comes the theme of my praise in the great assembly;
before those who fear you will I fulfill my vows.
26 The poor will eat and be satisfied;
they who seek the LORD will praise him—
may your hearts live forever!
27 All the ends of the earth
will remember and turn to the LORD,
and all the families of the nations
will bow down before him,
28 for dominion belongs to the LORD
and he rules over the nations.
29 All the rich of the earth will feast and worship;
all who go down to the dust will kneel before him—
those who cannot keep themselves alive.
30 Posterity will serve him;
future generations will be told about the Lord.
31 They will proclaim his righteousness
to a people yet unborn—
for he has done it.
Does it remind you of something?