Clause 7: Salary / Clause 8: Oath or affirmation
The President shall, at stated Times, receive for his Services, a Compensation, which shall neither be increased nor diminished during the Period for which he shall have been elected, and he shall not receive within that Period any other Emolument from the United States, or any of them.
The president's salary, currently $400,000 a year, must remain constant throughout the president's term. The president may not receive other compensation from either the federal or any state government.
Clause 8: Oath or affirmation.
Before he enter on the Execution of his Office, he shall take the following Oath or Affirmation:—"I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States."
According to the Joint Congressional Committee on Presidential Inaugurations, George Washington added the words "So help me God" during his first inaugural, though this has been disputed. There are no contemporaneous sources for this fact, and no eyewitness sources to Washington's first inaugural mention the phrase at all—including those that transcribed what he said for his oath.
Also, the president-elect's name is typically added after the "I", for example, "I, George Washington, do...." Normally, the chief justice of the United States administers the oath. It is sometimes asserted that the oath bestows upon the president the power to do whatever is necessary to "preserve, protect and defend the Constitution." Andrew Jackson, while vetoing an Act for the renewal of the charter of the national bank, implied that the president could refuse to execute statutes that he felt were unconstitutional. In suspending the privilege of the writ of habeas corpus, President Abraham Lincoln claimed that he acted according to the oath. His action was challenged in court and overturned by the U.S. Circuit Court in Maryland (led by Chief Justice Roger B Taney) in Ex Parte Merryman, (1861). Lincoln ignored Taney's order. Finally, Andrew Johnson's counsel referred to the theory during his impeachment trial. Otherwise, few have seriously asserted that the oath augments the president's powers.
The vice president also has an oath of office, but it is not mandated by the Constitution and is prescribed by statute. Currently, the vice presidential oath is the same as that for members of Congress and members of the Cabinet.
I do solemnly swear (or affirm) that I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion; and that I will well and faithfully discharge the duties of the office on which I am about to enter. So help me God