What was one reason why lincoln pushed for passage of the thirteenth amendment?

The Thirteenth Amendment to the Constitution of the United States officially abolished and continues to prohibit slavery in the United States of America, and, with limited exceptions (such as those convicted of a crime) prohibited involuntary servitude.

At the time of ratification, slavery remained legal only in Delaware, Kentucky, Missouri, Maryland and New Jersey. In the rest of the United States slaves had been released by state action and the "Emancipation Proclamation" of the federal government.  

Abraham Lincoln (who had promulgated the Proclamation) and others were concerned that the Emancipation Proclamation would be seen as a temporary measure only during the Civil War, and, therefore, in addition to the liberation of slaves in those states where slavery was still legal, they supported the Amendment as a means of guaranteeing the permanent abolition of slavery.

during the debate over his landmark energy policy proposal, president jimmy carter failed to consult one of the most powerful senators, louisiana’s russell long, who would have a big say over whether the legislation moved through the upper chamber. this was classic carter. with a strong distaste for congressional politics, the president simply refused to do what most other presidents would consider routine, such as courting key senators. long became so irate with the president that when he was finally invited to a white house dinner, he stood up to ask a question and, before doing so, proceeded to sarcastically introduce himself: “i’m russell long, chairman of the senate finance committee.”

this interaction is a revealing moment in stuart e. eizenstat’s fascinating new history of carter’s presidency. the former peanut farmer from georgia was a president who, according to conventional wisdom, didn’t care much for party politics; nonetheless, in eizenstat’s view, carter’s legacy on domestic and foreign policy has been vastly underappreciated. the author paints carter as a “bold and determined” leader who bravely attacked the challenges of his time. eizenstat goes so far as to argue that carter might very well be the most successful one-term president in american history.