And the Lord spake unto Moses
Either whilst the plague upon the waters continued, or immediately upon the removal of it:
go unto Pharaoh, and say unto him, thus saith the Lord, let my
people go, that they may serve me;
mentioning neither time nor place, where, when, and how long they should serve him, for which their dismission was required, but insist on it in general.
The Brenton translation of the Septuagint is in the public domain.