A covering - Hebrew "the covering," perhaps "the hanging" or "awning" at the door of the house, as the word seems to mean when spoken of the tabernacle.
Ground corn - Or "peeled barley," which she spread out as if for the purpose of drying it in the sun.

And (h) the woman took and spread a covering over the well's mouth, and spread ground corn thereon; and the thing was not known.
(h) Thus God sends help to his, in their greatest dangers.

And the woman took and spread a covering over the well's mouth,.... This woman, very probably, was the man's wife of the house, as Abarbinel notes; who took a cloth, and spread it over the well's mouth, that it could not be seen or known that there was a well there:
and spread ground corn thereon: just taken out of the mill, before it was sifted, while in the bran; or corn unhusked, or just threshed out, in order to be dried in the sun, and then parched; or wheat bruised for that purpose: Josephus says (q) they were locks of wool she spread:
and the thing was not known; that the young men were in the well.
(q) Antiqu. l. 7. c. 9. sect. 7.

And the man's wife spread a covering (המּסך, the covering which she had close at hand) over the well (over the opening into the cistern), and scattered groats (ריפות, peeled barley: Proverbs 27:22) upon it, so that nothing was noticed. The Vulgate explanation is a very good one: "quasi siccans ptisanas" (as if drying peeled barley).

Spread corn - Under pretence of drying it by the sun: which shews it was summer - time.