Isaiah 19:20

for a sign and for a witness unto the Lord of hosts i.e. a reminder that He has a people in Egypt, and that by their presence the land is consecrated to Him.

The process of conversion in this and the following verses is finely conceived. First, the name of Jehovah is made known by the religious observances of the Jewish colonists and proselytes; then, in a time of trouble, the Egyptians turn to Him instead of to their false gods, and learn to know Him through His answer to their prayers (20, 21); finally this experience of Jehovah is deepened and purified by a discipline similar to that to which Israel was subjected in the time of the Judges (22).

the oppressors Omit the art.; the reference is quite general.

a saviour See Judges 3:9; Judges 3:15; 2 Kings 13:5.

a great one Better: a champion. A special allusion to Ptolemy Soter, or to the Jewish generals who served under Ptolemy Philometor is not called for.