Background

Following the death of President von Hindenburg in August 1934, Adolf Hitler assumed power as Reich Chancellor and Führer. Shortly thereafter, on August 20, 1934, the longstanding oath taken by state officials was changed so that they no longer swore loyalty to the German constitution but rather to Hitler as head of state.

Although in retrospect this change seems to indicate another step in Hitler's consolidation of power, at the time many would have understood it differently. By replacing “Constitution” with “Hitler,” the oath was meant to convey that Hitler's will was the same as that of the nation and the people and that his will could not, by definition, contradict the imperative to “observe the law and conscientiously fulfill the duties” of office. In this way, the oath appeared to equate Hitler's authority with the constitution and to ensure that it would be limited by the primacy of law and duty in public office.

Translations

Oath  of Loyalty for All State Officials as of August 14, 1919:
“I swear loyalty to the Constitution, obedience to the law, and conscientious fulfillment of the duties of my office, so help me God.” 
[Translated from Reichsgesetzblatt I, 1919, pp. 1419-1420.]

Oath  of Loyalty for All State Officials as of August 20, 1934:
“I swear I will be true and obedient to the Führer of the German Reich and people, Adolf Hitler, observe the law, and conscientiously fulfill the duties of my office, so help me God.” 9
[Translated from Reichsgesetzblatt I, 1934, p. 785.]