Ye shall eat, &c. No seed would be sown on account of the (foretold) devastation wrought by the invasion. Hezekiah refers to this "sign" in his "Songs of the Degrees" (Psa_126:5, Psa_126:6; Psa_128:2).
groweth of itself. Reference to Pentateuch (Lev_25:5, Lev_25:11). Only here, 2Ki_19:29, and Job_14:19.
springeth of the same = shooteth up of itself, or from the roots. Hebrew. shahith, occurs only here.