Or HaChaim on Exodus 6:10/אור החיים על שמות ו׳:י׳

1ויאמר…. בא דבר אל פרעה, He said:" come and speak sternly with Pharaoh, etc." Moses was to tell Pharaoh that G'd had instructed him to speak to Pharaoh and to demand that he should let the Jewish people depart from his land. The letter ו at the beginning of the word וישלח is significant because it does not make sense as a conjunctive letter; nothing else had been demanded prior to that in the conversation described. It must therefore refer to Moses telling Pharaoh that his first instruction had been to tell him that he spoke at the behest of G'd. It was quite an event that an ordinary individual should present himself at court without invitation and make demands on the Monarch. The manner in which these demands were to be made was even more astounding.

2Moreover, it appears that Moses was to demand not only that Pharaoh should not object if the Israelites would leave of their own accord, but he was to demand that Pharaoh actually give them a "send-off."