Don't grieve. Anything you lose comes round in another form.

The familiar English wording appears in Coleman Barks's The Essential Rumi (1995, p. 272). Barks works from earlier scholarly translations rather than the Persian, and his renderings are interpretive versions in his own poetic voice, so the sentence people quote is best understood as Barks's rendering of a poem presented as Rumi's, not a verbatim line from Rumi himself. The underlying sentiment — that loss is not permanent and what we lose returns transformed — is central to Rumi's Sufi thought, and no competing author or earlier origin exists. We classify it as attributed; verification would require matching the line to a specific numbered passage in the Persian corpus (Masnavi or Divan-e Shams).