מדרש על תרומות 11:4

11) ("It should have been written )"for (holy) bread." (Why) "his bread"? (To teach that) he sifts the flour as he wishes and perforates the greens as much as he wishes. I might think that the remnants of the perforated greens are rendered profane (not holy); it is, therefore, written "it is his bread" — it remains in its holiness.