Lincoln promised to compensate slave owners who were not in rebellion as of January 1, 1863 because he hoped to draw some rebels back to the Union.
In his Preliminary Emancipation Proclamation, Lincoln ordered to free slaves as a solution to the rebellion against the United States. Moreover, he added that if the Confederate states returned to the Union, slavery in those states would remain intact. However, Lincoln thought that the rebellion could not have existed without slavery; therefore, he also offered compensation to those people that adopted immediate abolishment of slavery.