Luk 13:24-27 "Strive" to enter in at the strait gate: for many, I say unto you, will seek to enter in, and shall not be able.
When once the master of the house is risen up, "and hath shut to the door", and ye begin to stand without, and to knock at the door, saying, "Lord, Lord", open unto us; and he shall answer and say unto you, I know you not whence ye are: then shall ye begin to say, We have eaten and drunk in thy presence, and thou hast taught in our streets. But he shall say, I tell you, I know you not whence ye are; depart from me, all ye workers of iniquity.
"Lord, Lord" - Mat 7:21 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
Mat 7:22 Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works?
"And hath shut the door" - Mat 25:10-12 And while they went to buy, the bridegroom came; and they that were ready went in with him to the marriage: and the door was shut. Afterward came also the other virgins, saying, Lord, Lord, open to us.
Mat 25:12 But he answered and said, Verily I say unto you, I know you not.
"Strive" - from Torrey's 'Treasury of Scripture Knowledge' -
Luk 21:36 Watch ye therefore, and pray always, that ye may be accounted worthy to escape all these things that shall come to pass, and to stand before the Son of man.
Mat 11:12 And from the days of John the Baptist until now the kingdom of heaven suffereth violence, and the violent take it by force.
John 6:27 Labour not for the meat which perisheth, but for that meat which endureth unto everlasting life, which the Son of man shall give unto you: for him hath God the Father sealed.
1Co 9:24-27 Know ye not that they which run in a race run all, but one receiveth the prize? So run, that ye may obtain. And every man that striveth for the mastery is temperate in all things. Now they do it to obtain a corruptible crown; but we an incorruptible. I therefore so run, not as uncertainly; so fight I, not as one that beateth the air: but I keep under [buffet] my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway. 7
Phi 2:12, 13 Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling. For it is God which worketh in you both to will and to do of his good pleasure.
Col 1:29 Whereunto I also labour, striving according to his working, which worketh in me mightily.
Heb 4:11 Let us labour therefore to enter into that rest, lest any man fall after the same example of unbelief.
2Pe 1:4-10 Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust. And beside this, giving all diligence, add to your faith virtue; and to virtue knowledge; and to knowledge temperance; and to temperance patience; and to patience godliness; and to godliness brotherly kindness; and to brotherly kindness charity. For if these things be in you, and abound, they make you that ye shall neither be barren nor unfruitful in the knowledge of our Lord Jesus Christ.
But he that lacketh these things is blind, and cannot see afar off, and hath forgotten that he was purged from his old sins.
Wherefore the rather, brethren, give diligence to make your calling and election sure: for if ye do these things, ye shall never fall
1Jn 2:5 But whoso keepeth His Word, in him verily is the love of God perfected: hereby know we that we are in Him.