Article II, Section 3:
He shall from time to time give to the Congress Information of the State of the Union, and recommend to their Consideration such Measures as he shall judge necessary and expedient; he may, on extraordinary Occasions, convene both Houses, or either of them, and in Case of Disagreement between them, with Respect to the Time of Adjournment, he may adjourn them to such Time as he shall think proper; he shall receive Ambassadors and other public Ministers; he shall take Care that the Laws be faithfully executed, and shall Commission all the Officers of the United States.
The power to commission officers, as applied in practice, does not mean that the President is under constitutional obligation to commission those whose appointments have reached that stage, but merely that it is he and no one else who has the power to commission them, and that he may do so at his discretion. Under the doctrine of Marbury v. Madison, the sealing and delivery of the commission is a purely ministerial act which has been lodged by statute with the Secretary of State, and which may be compelled by mandamus unless the appointee has been in the meantime validly removed. 1 By an opinion of the Attorney General many years later, however, the President, even after he has signed a commission, still has a locus poenitentiae and may withhold it; nor is the appointee in office till he has this commission. 2 This is probably the correct doctrine. 3