Matthew 3.9 states don’t think you can say to yourselves we have Abraham as our father.
John commanded those who were seeking God to repent and to do deeds proving their repentance. Their position was not sufficient for saving them.
The religious thought having the right lineage was all God required but God requires right living defined by obedience to His Son the Savior Jesus.
Many today expect to enter heaven because they believe in God and even attend church but they ignore the Scriptures that teach them how to please God and so they live lives in opposition to the clear teaching of Jesus.
Demons believe in God but disobey Him even working against Him to kill and destroy. So too the Lord Jesus taught that those who were not with Him were working against Him.
The expectation of God is that those who seek Him obey Him and give their lives to fulfilling His purposes on the earth.
This is why Jesus commanded those who would come to Him must deny themselves by taking their cross and following Him. Submitting ourselves to Jesus is God’s expectation of His people.
This surrender to the Lordship of Jesus begins by repenting from evil through confession and admission then acknowledging Jesus as Lord through word and deed.
Those who will spend eternity with God in heaven are those who are now spending time with Him on earth seeking Him and serving Him so that His kingdom might come to earth as it is in heaven.
Knowing is not the same as doing; we are required to know God and do His will.