Our concern encounters it as this thing that is ready-to-hand . To the extent that any entity shows itself to concern2—that is, to the extent that it is discovered in its Being—it is already something ready-to-hand environmentally; it just is not 'proximally' a 'world-stuff' that is merely present-at-hand.
As the Being of something ready-to-hand, an involvement is itself discovered only on the basis of the prior discovery of a totality of involvements. So in any involvement that has been discovered (that is, in anything ready-to-hand which we encounter) , what we have called the "worldly character" of the ready-to-hand has been discovered beforehand. In this totality of involvements which has been discovered beforehand, there lurks an ontological relationship to the world. In letting entities be involved so that they are freed for a totality of involvements, one must have disclosed already that for which [ woraufhin] they have been freed. But that for which something environmentally ready-to-hand has thus been freed (and indeed in such a manner that it becomes accessible as an entity within-the-world first of all) , cannot itself be conceived as an entity with this discovered kind of Being. It is essentially not discoverable, if we henceforth reserve "discoveredness" as a term for a possibility of Being which every entity without the character of Dasein may possess.
But what does it mean to say_ that that for which3 entities within-the-world are proximally freed must have been previously disclosed? To Dasein's Being, an understanding of Being belongs. Any understanding [Verständnis] has its Being in an act of understanding [Verstehen].  If Being-in-the-world is a kind of Being which is essentially befitting to Dasein, then to understand Being-in-the-world belongs to the essential content of its understanding of Being. The previous disclosure of that for which what we encounter within-the-world is subsequently freed,4 amounts to nothing else than understanding the world—that world towards which Dasein as an entity always comports itself.
Whenever we let there be an involvement with something in something beforehand, our doing so is grounded in our understanding such things as letting something be involved, and such things as the "with-which" and the "in-which" of involvements. Anything of this sort, and anything else that is basic for it, such as the "towards-this" as that in which there is an involvement, or such as the "for-the-sake-of-which" to which every "towards-which" ultimately goes back5—all these must be disclosed beforehand with a certain intelligibility [Verständlichkeit].
2 Here we follow the newer editions in reading: 'Sofern sich ihm überhaupt ein Seiendes zeigt ...'. The older editions read 'Sofern sich mit ihm ...', which is somewhat ambiguous but suggests that we should write : 'To the extent that with what is ready-to-hand any entity shows itself ...'.
3 'Worauf'. The older editions have 'woraufhin'.
4 'Das vorgängige Erschliessen dessen, woraufhin die Freigabe des innerweltlichen Begegnenden erfolgt ...'
5 '... wie das Dazu, als wobei es die Bewandtnis hat, das Worum-willen, darauf letztlich alles Wozu zurückgeht.' The older editions have '... als wobei es je die Bewandtnis hat ...' and omit the hyphen in 'Worum-willen'.