a sense of mutual obligation to support one another

at one’s disposal

at one’s command

at one’s best

astern of one’s reckoning

as fast as one’s legs could carry

as black as one’s hat

are frantically cutting one another’s throats

apply one’s mind to

apple of one’s eyes

apple of one’s eye

annul one’s position

and lengthening one’s life

all sorts of feelings well up in one's heart

all one's life

all one’s life

air one’s opinion

ahead of one’s times