70 ILCS 1210/24
No person who holds any public office, or who has been nominated for, or who seeks a nomination or appointment to any public office, shall corruptly use or promise to use, either directly or indirectly, any official authority or influence in order to secure or aid any person in securing for himself or for another, any office or public employment, or any nomination, confirmation, promotion or increase of salary as a reward for political influence or service. No person appointed, or about to be appointed to the position of civil service commissioner, or to a position in the classified service, shall execute or sign a resignation in advance, dated or undated, for the purpose, or with the result of permitting the appointing power to create at his will a vacancy in the office of civil service commissioner or in a position in the classified service.
70 ILCS 1210/24