Exodus 8:20

And the Lord said unto Moses, rise up early in the morning,
&c.] Of the day following, the twenty eight of Adar, or February, according to Bishop Usher; this was the fittest time to meet with Pharaoh, and the most likely to make impressions on him:

and stand before Pharaoh:
meet him as he comes along, and stop him, and stand before him as having something to say to him; this was using great boldness and freedom with a king; but as Moses was ordered to do it by the King of kings, it became him to obey him:

lo, he cometh forth to the water; (See Gill on Exodus 7:15)

and say unto him, thus saith the Lord, let my people go, that they may
serve me;
which had often been required before, but to no purpose, and in case of refusal he is threatened as follows.