Preach the word; be instant in season, out of season.

-Bible (NewTestament)
  Timothy 4:2.

The services of a menial servant, taking him as an example of unproductive labour,'generally perish in the very instant of their performance'öand forthwith into this galley, along with the menial servant, goes the sovereign, accompanied by all the army, the navy, and the civil service, followed by churchmen, lawyers, buffoons and opera dancers. All theseöand it is a hard sayingörender services which perish in the very instant of their performance. 368

-Gray, Alexander
The Development of Economic Doctrine.

I said,'Forgive me, sir,'and plucked the cigar out of his mouth. By the time I got back to my camera, he looked so belligerent he could have devoured me. It was at that instant that I took the photograph. The silence was deafening.

-Karsh,Yousuf
  Recalling how he snapped the celebrated 'bulldog' photograph of Sir Winston Churchill in the Speaker's Chambers, House of Commons, Ottawa, on 30 Dec1941. Karsh:  A Fifty-Year Retrospective.

   The stubborn spearmen still made good Their dark impenetrable wood, Each stepping where his comrade stood The instant that he fell.

-Scott, Sir Walter
  Marmion, canto 6, stanza 34.