You said that we have 'sinned in the past'?
What about the sin you commit in the present and you will commit in the future?
Are you sinning right now in the present?
John said if we sin and we confess our sins we are cleansed
But John did write this
1 John 2:1. My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous:”
“ 1 John 3:6. Whosoever abideth in him sinneth not: whosoever sinneth hath not seen him, neither known him.”
1 John 1:6. If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth:”
Paul also said, free from sin
Romans 6:18. Being then made free from sin, ye became the servants of righteousness.”
Peter also said,
1 Peter 4:1. Forasmuch then as Christ hath suffered for us in the flesh, arm yourselves likewise with the same mind: for he that hath suffered in the flesh hath ceased from sin;”
And Paul said to believers who some had fallen into sin,
1 Corinthians 6:9. Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind,10. Nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners, shall inherit the kingdom of God.”
And Paul said,
2 Corinthians 12:21. And lest, when I come again, my God will humble me among you, and that I shall bewail many which have sinned already, and have not repented of the uncleanness and fornication and lasciviousness which they have committed.”