"Invoke these Gods with fervour"

But before all, thy soul to its faithful duty,
Invoke these Gods with fervour, they whose aid,
Thy work begun, alone can terminate.

Excerpted from -
The Golden Verses of Pythagoras [1917] by Fabre d'Olivet

Source:
http://www.sacred-texts.com/cla/ogv/ogv37.htm