In a position of unity of feeling; in harmony, concord, or friendship; opposed to at variance, at odds. Sometimes implying a previous state of…

at (also in) unity: in agreement, concord, or harmony; in union; at one.

at peace: in a state of concord or friendliness; not at war or at variance (with a country, a person, oneself, etc.); in a state of quietness or…