Matthew 16:18
And I say to thee: That thou art Peter; and upon this rock I will build my church, and the gates of hell shall not prevail against it.
Roman Catholics will tell you that the message in the verse above was the beginning of their church. And Peter was that rock, their first Pope. (Peter was married. Unlike priests and pope's today).
In truth, Jesus was speaking of Himself there.
He, Jesus, is that rock.
Upon this rock, He is the cornerstone of the church, the rock, foundation. And the Gospel message is what would call the church, the community or body of faithful in Him, who have heard the word delivered by The Word made flesh.
Upon the rock that is Jesus the Good News invitation doth build a church. And the gates of Hell shall not prevail against it.
Gates? Why doesn't it simply say, Hell shall not prevail against it?
I think it important to interject here that our faith as Christians was grounded first in Judaism and the prophecies of our blessed Messiah.
We cannot come to understanding of the scriptures if we ignore the message in the first testament, what is called, the Old Testament.
Because the Old Testament prophecies what is to come, and the New Testament testifies as to what appeared.
Judaism is filled with symbolism in its tradition. Names are translated into numbers, for example. Numbers have meaning too of course. That's why if you read the Old Testament and the New you'll notice between them a recurrence of certain numbers. 3, 7, 10, like that.
Jesus ministry in Palestine was directed to the Jews. They who had their foundation on the Tanakh.
Let's look at verse 18 through the Orthodox Jewish Bible's teaching:
The Book of Mattityahu chapter 16:18
And I also say to you that you are Shimon Kefa [Petros] and upon this TSUR I will build my Kehillah, my Chavurah (the Community of Moshiach) and the shaarei Sheol (gates of Sheol) shall not overpower it.
*The Greek Interlinear Version has, hadēs, in place of Sheol. (found at link above)
What is Sheol?
As we know in His ministry Jesus used symbolism that the Jews would be familiar with so as to impart the full meaning of His words to them. He also repeated parables that they were familiar with, using a few tweeks here and there, so as to make the contemporary image apply to their present day understanding of places and things.
So, Sheol, what is it?
Sheol is the abode of the dead. A hopeless place in the lowest parts of the earth.
See here:
Bible Study Tools
..."Unlike this world, Sheol is devoid of love, hate, envy, work, thought, knowledge, and wisdom (
Ecclesiastes 9:6 Ecclesiastes 9:10 ). Descriptions are bleak: There is no light (
Job 10:21-22 ;
17:13 ;
Psalms 88:6 Psalms 88:12 ;
143:3 ), no remembrance (
Psalm 6:5 ;
88:12 ;
Eccl 9:5 ), no praise of God (
Psalm 6:5 ;
30:9 ;
88:10-12 ;
115:17 ;
Isa 38:18 ) — in fact, no sound at all (
Psalm 94:17 ;
115:17 ).
Its inhabitants are weak, trembling shades (
Job 26:5 ;
Psalm 88:10-12 ;
Isa 14:9-10 )
who can never hope to escape from its gates (
Job 10:21 ;
17:13-16 ;
Isa 38:10 ).
Sheol is like a ravenous beast that swallows the living without being sated (
Prov 1:12 ;
27:20 ;
Isa 5:14 ). Some thought the dead were cut off from God (
Psalm 88:3-5 ;
Isa 38:11 ); while others believed that God's presence reached even to Sheol (
Psalm 139:8 ).
Toward the end of the Old Testament, God revealed that there will be a resurrection of the dead (
Isa 26:19 ). Sheol will devour no longer; instead God will swallow up Death (
Isa 25:8 ). The faithful will be rewarded with everlasting life while the rest will experience eternal contempt (
Dan 12:2 ). This theology developed further in the intertestamental period....
[continues here]
Now we can read Matthew's verse 18 in light of that understanding.
And I say to thee: That thou art Peter; and upon this rock I will build my church, and the gates of hell shall not prevail against it.
(As an aside, since "gates" was used in the OP Bible version of Matthew, I thought this would be of added interest for those who can't get enough of Bible study: The Symbolism of the Ten Gates of Ancient Jerusalem - Part 1) This study goes through to 4 parts. There is no link to part 2 at the end of that article, as the next parts arrived at different times rather than being published in one large collection. To go to the next part just go to your browser window and replace, 1, as in part 1 in the address there, with 2. And so forth all the way to the 4th part. )