Christ, when here on earth said: "He that entereth not by the door into the sheepfold, but climbeth up some other way, the same is a thief and a robber." John 10:1. He insisted that He Himself was the door of salvation, saying: "I am the door: by Me if any man enter in, he shall be saved." John 10:9. Certainly no one should have difficulty in finding the door to heaven, seeing there is only one. The door is not such things as baptism, church membership, or good works. It is a Person—just one Person—the Lord Jesus Christ! All that any church, preacher, or priest can do to save men, is to point them to Him—the only door.
But this door, which is open now, will soon he shut, Jesus warned men: "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 to us; and He shall answer and say unto you, I know you not whence ye are... depart from Me all workers of iniquity.”
The Lord Jesus counseled His hearers to "strive [agonize] to enter in at the strait gate" (Luke 13:24, 25, 27). A "door" or "gate," we understand, is just an entrance; so Christ is the entrance to heaven as He said: "By Me if any man enter in, he shall be saved.”
When one puts his faith in, and depends wholly upon, the Lord Jesus Christ for salvation, he has entered the door. He is saved, and knows on the authority of God's Word that he will be in heaven.
"Verily, verily, I say unto you, He that heareth My Word, and believeth on Him that sent Me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life." John 5:24.
Every sinner is invited to enter this door. The Savior has promised: "Him that cometh to Me; I will in no wise cast out." John 6:37. He stands ready to receive and to bless every soul who comes to Him.