How do you get obtain the promise land out of phrase "partaker of Christ".
Because Hebrews 3 is not the only chapter in the entirety of the book. It's telling a story. Hebrews 3 is speaking of the same Jews in Hebrews 11.
The promise wasn't just land, it was also family. (Heb 6:13-15 When God made his promise to Abraham, since there was no one greater for him to swear by, he swore by himself, 14saying, “I will surely bless you and give you many descendants.”d 15And so after waiting patiently, Abraham received what was promised.)
I thought you were knowledgeable on the blood of Christ? (Heb 9:15 For this reason Christ is the mediator of a new covenant, that those who are called may receive the promised eternal inheritance—now that he has died as a ransom to set them free from the sins committed under the first covenant.)
We are not holy because of (our) works, we are made holy through the cross and the works of Jesus. (Heb 10:8-10 First he said, “Sacrifices and offerings, burnt offerings and sin offerings you did not desire, nor were you pleased with them”—though they were offered in accordance with the law. 9Then he said, “Here I am, I have come to do your will.” He sets aside the first to establish the second. 10And by that will, we have been made holy through the sacrifice of the body of Jesus Christ once for all.)
Jesus died for past/present/future sins. (Heb 10:11:14 Day after day every priest stands and performs his religious duties; again and again he offers the same sacrifices, which can never take away sins. 12But when this priest had offered for all time one sacrifice for sins, he sat down at the right hand of God, 13and since that time he waits for his enemies to be made his footstool. 14For by one sacrifice he has made perfect forever those who are being made holy.)