be at

be at

v.
1. To be located somewhere: The hotel is at the center of town. I am at the corner of 11th Street and Third Avenue.
2. To take place at some given time: Our meeting is at noon. The movie is at 8:00, so we've got plenty of time for dinner.
3. To be busy trying to accomplish something; keep at. Often used with it: I have been at this interminable project for weeks now.
4. To remind someone regularly about something or to do something: He's been at me about the book he lent to me.
References in classic literature ?
I have sent for you to ask that my pocket-book, dressing-case, and clothes be at once restored to me, and that I be provided with the means of continuing my journey without a moment's further delay.
they do not know, and cannot tell; but in order that they may not appear to be at a loss, they repeat the ready-made charges which are used against all philosophers about teaching things up in the clouds and under the earth, and having no gods, and making the worse appear the better cause; for they do not like to confess that their pretence of knowledge has been detected-- which is the truth; and as they are numerous and ambitious and energetic, and are drawn up in battle array and have persuasive tongues, they have filled your ears with their loud and inveterate calumnies.
Three months ago, therefore, I went out to meet him as a knight-errant, under the assumed name of the Knight of the Mirrors, intending to engage him in combat and overcome him without hurting him, making it the condition of our combat that the vanquished should be at the disposal of the victor.
Peace, Sancho," said Don Quixote; "thou seest my suspension and retirement is not to exceed a year; I shall soon return to my honoured calling, and I shall not be at a loss for a kingdom to win and a county to bestow on thee.
They, being born, must die, and, being dead, are glad to be at rest.
But here through the dusk comes one who is not glad to be at rest.