The answer is:
He states that no act of the living can in any way compare to that of the brave men who died for the cause here.
In his 1863 speech "The Gettysburg Address," president Abraham Lincoln makes reference to the soldiers and citizens who perished during the American Civil War. Therefore, he states that the ground could not be more sacred because the people who gave their lives there already sanctified it with their deaths. As a result, he encourages soldiers to continue to fight for the unity of the nation.