Matthew 7:14

For narrow is the gate, and straitened the way, that leadeth unto life, and few are they that find it.

Acts 14:22

confirming the souls of the disciples, exhorting them to continue in the faith, and that through many tribulations we must enter into the kingdom of God.

Proverbs 4:26-27

Make level the path of thy feet, And let all thy ways be established.

Proverbs 8:20

I walk in the way of righteousness, In the midst of the paths of justice;

Isaiah 30:21

and thine ears shall hear a word behind thee, saying, This is the way, walk ye in it; when ye turn to the right hand, and when ye turn to the left.

Isaiah 35:8

And a highway shall be there, and a way, and it shall be called The way of holiness; the unclean shall not pass over it; but is shall be for the redeemed : the wayfaring men, yea fools, shall not err therein .

Isaiah 57:14

And he will say, Cast ye up, cast ye up, prepare the way, take up the stumbling-block out of the way of my people.

Jeremiah 6:16

Thus saith Jehovah, Stand ye in the ways and see, and ask for the old paths, where is the good way; and walk therein, and ye shall find rest for your souls: but they said, We will not walk therein .

Matthew 16:24-25

Then said Jesus unto his disciples, If any man would come after me, let him deny himself, and take up his cross, and follow me.

Matthew 20:16

So the last shall be first, and the first last.

Matthew 22:14

For many are called, but few chosen.

Matthew 25:1-12

Then shall the kingdom of heaven be likened unto ten virgins, who took their lamps, and went forth to meet the bridegroom.

Mark 8:34

And he called unto him the multitude with his disciples, and said unto them, If any man would come after me, let him deny himself, and take up his cross, and follow me.

Luke 12:32

Fear not, little flock; for it is your Father's good pleasure to give you the kingdom.

Luke 13:23-30

And one said unto him, Lord, are they few that are saved? And he said unto them,

John 15:18-20

If the world hateth you, ye know that it hath hated me before it hated you.

John 16:2

They shall put you out of the synagogues: yea, the hour cometh, that whosoever killeth you shall think that he offereth service unto God.

John 16:33

These things have I spoken unto you, that in me ye may have peace. In the world ye have tribulation: but be of good cheer; I have overcome the world.

Romans 9:27-29

And Isaiah crieth concerning Israel, If the number of the children of Israel be as the sand of the sea, it is the remnant that shall be saved:

Romans 9:32

Wherefore? Because they sought it not by faith, but as it were by works. They stumbled at the stone of stumbling;

Romans 11:5-6

Even so then at this present time also there is a remnant according to the election of grace.

Romans 12:2

And be not fashioned according to this world: but be ye transformed by the renewing of your mind, and ye may prove what is the good and acceptable and perfect will of God.

Ephesians 2:2-3

wherein ye once walked according to the course of this world, according to the prince of the powers of the air, of the spirit that now worketh in the sons of disobedience;

1 Thessalonians 3:2-5

and sent Timothy, our brother and God's minister in the gospel of Christ, to establish you, and to comfort you concerning your faith;

1 Peter 3:20-21

that aforetime were disobedient, when the longsuffering of God waited in the days of Noah, while the ark was a preparing, wherein few, that is, eight souls, were saved through water:

Treasury of Scripture Knowledge

Summary

Because strait is the gate, and narrow is the way, which leadeth unto life, and few there be that find it.

Bible References

Because

Matthew 16:24
Then said Jesus unto his disciples, If any man would come after me, let him deny himself, and take up his cross, and follow me.
Proverbs 4:26
Make level the path of thy feet, And let all thy ways be established.
Proverbs 8:20
I walk in the way of righteousness, In the midst of the paths of justice;
Isaiah 30:21
and thine ears shall hear a word behind thee, saying, This is the way, walk ye in it; when ye turn to the right hand, and when ye turn to the left.
Isaiah 35:8
And a highway shall be there, and a way, and it shall be called The way of holiness; the unclean shall not pass over it; but is shall be for the redeemed : the wayfaring men, yea fools, shall not err therein .
Isaiah 57:14
And he will say, Cast ye up, cast ye up, prepare the way, take up the stumbling-block out of the way of my people.
Jeremiah 6:16
Thus saith Jehovah, Stand ye in the ways and see, and ask for the old paths, where is the good way; and walk therein, and ye shall find rest for your souls: but they said, We will not walk therein .
Mark 8:34
And he called unto him the multitude with his disciples, and said unto them, If any man would come after me, let him deny himself, and take up his cross, and follow me.
John 15:18
If the world hateth you, ye know that it hath hated me before it hated you.
John 16:2
They shall put you out of the synagogues: yea, the hour cometh, that whosoever killeth you shall think that he offereth service unto God.
Acts 14:22
confirming the souls of the disciples, exhorting them to continue in the faith, and that through many tribulations we must enter into the kingdom of God.
1 Thessalonians 3:2
and sent Timothy, our brother and God's minister in the gospel of Christ, to establish you, and to comfort you concerning your faith;

General references

Numbers 4:48
even those that were numbered of them, were eight thousand and five hundred and fourscore.
Proverbs 2:9
Then shalt thou understand righteousness and justice, And equity, yea , every good path.
Proverbs 14:12
There is a way which seemeth right unto a man; But the end thereof are the ways of death.
Matthew 22:14
For many are called, but few chosen.
Romans 3:17
And the way of peace have they not known:

American Standard Version Public Domain