how do I exclude a commit from set of commits to be pushed.

In the series of commits C1..C8 how do I exclude a commit to be pushed.

use case - I have commits say C1..C8 to be pushed. Due to my pre-receive hook commit C4 is complying with commit standard. I have amended C4 to C5 ; still C4 shows up in commits to be pushed list.

git reflog delete --rewrite and git gc --prune did not help

Thx/ Mahesh --