I am the vine, ye are the branches: He that abideth in Me, and I in him, the same bringeth forth much fruit: for without Me ye can do nothing. -John 15:5

We believe that the more a man knows and feels himself to be one with Jesus, the more holy will he be. The very fact that Christ and the Christian become one, makes the Christian Christ-like. Why is a Christian’s character like Christ’s character? Only for this reason, that he is joined and united to the Lord Jesus Christ. Why doth that branch bring forth grapes? Simply because it has been engrafted into the vine, and therefore it partakes of the nature of the stem. So, Christian, the only way whereby thou canst bring forth fruit to God is by being grafted into Christ and united with Him. You Christians who think you can walk in holiness without keeping up perpetual fellowship with Christ have made a great mistake. If you would be holy, you must live close to Jesus. Good works spring only thence. Hence we draw the most powerful reasons against anything like trusting in works; for as works are only the gift of God, how utterly impossible does it become for an unrighteous, unconverted, ungodly man, to produce any such good works in himself. And if they are God’s gifts, how little merit can there be in them.

So we say, good works are the best evidence of spiritual life in the soul. Is it not written, “We know that we have passed from death unto life, because we love the brethren?” Loving the brethren is a good work. Again, “If any man abide in Me, he shall bring forth fruit.” Fruits of righteousness are good works, and they are evidence that we abide in Christ. If I am living in sin day by day, what right have I to conclude I am a child of God?~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0070.cfm