Thank you for that thoughtful question. There are two texts in the Bible that I believe you are referring to. “Because strait [is] the gate, and narrow [is] the way, which leadeth unto life, and few there be that find it.” Matthew 7:14. “Strive to enter in at the strait gate: for many, I say unto you, will seek to enter in, and shall not be able.” Luke 13:24.
Heaven is such a wonderful place that “eye has not seen, nor ear heard, neither has it entered into the heart of man the things which God has prepared for them that love Him.” I Corinthians 2:9. Isaiah 65:21 describes our home as real. We will build houses and live in them and plant vineyards and eat the fruit.
In the capital city, the New Jerusalem, the gates are made of one pearl, the streets are paved with gold, the walls of the city are made of jasper, and the River of Life runs right through the middle with the Tree of Life on either side of the River. How beautiful it must be. Not only is there physical beauty, but also peace and tranquility. “They shall not hurt nor destroy in all my holy mountain: for the earth shall be full of the knowledge of the Lord, as the waters cover the sea.” Isaiah 11:9. It is worth striving for.
But what if this beautiful place was ruined with pain, sickness, sorrow, death and hatred? What would be gained by Jesus dying on the cross to save us? What would our salvation be worth, just to change locations for the gold and riches of heaven?
Heaven has suffered from the very inception of sin. God and Christ have suffered beyond description, as have the angels in their sympathy for their Lord and for the human race. God hates sin and cannot afford to allow it to enter heaven again.
God is faced with a problem then—how to save the sinner without retaining the sin. Before God can take us home, we must eradicate sin from our lives. He wants to help us do this, for without Him, it would be a hopeless endeavor.
It is not an easy road, but it will be worth it. We have the assurance of Jesus’ presence to help us along the path to the narrow gate. No matter the cost, we will agree that “heaven is cheap enough.” Our calling is to strive to become like Christ and trust Him to work in our lives. Indeed, few are willing to give their whole hearts to Christ, yet there is no cost so great that heaven is not greater still.