Here is what I've previously written about Jefferson writing to Washington. If you prefer another source, Google can lead you to the whole letter.

https://medium.com/black-history-month-365/thomas-jeffersons-four-percent-solution-5b9f1e173ef2#:~:text=The%20real%2Dlife%20Thomas%20Jefferson,slave%20trade%20as%20%E2%80%9Cexecrable%20commerce%20%E2%80%A6

The 1808 date was set in the Constitution as the first available date for ending the International Slave Trade. You may choose to believe it was always the American intent to end slavery. I watch what they did, not what they said.