1;  God threatens to send locusts.
  7;  Pharaoh moved by his servants, inclines to let the
     Israelites go.
 12;  The plague of the locusts.
 16;  Pharaoh entreats Moses.
 21;  The plague of darkness.
 24;  Pharaoh again entreats Moses, but yet is hardened.

 * I have hardened.
  4:21  7:13,14  9:27,34,35  Ps 7:11 
 * that I.
  3:20  7:4  9:16  14:17,18  15:14,15  Jos 2:9,10  4:23,24  1Sa 4:8 
  Ro 9:17