Allahu Abha should be found upon the lips everytime

The Greatest Name should be found upon the lips in the first awakening moment of early dawn. It should be fed upon by consistent use in daily invocation, in trouble, under opposition, and should be the last word breathed when the head rests upon the pillow at night. It is the name of comfort, protection, happiness, illumination, love and unity.

(‘Abdu’l-Bahá, Wisdom of the Master, p. 58)

The Greatest Name is Alláh-u-Abhá.

— Shoghi Effendi, Unfolding Destiny, p. 369