Exodus 3:12

12He said, a  But I will be with you, and this shall be the sign for you, that I have sent you: when you have brought the people out of Egypt, b  you shall serve God on this mountain.”

Exodus 3:18

18And c  they will listen to your voice, and you and the elders of Israel d  shall go to the king of Egypt and say to him, ‘The  Lord, the God of the Hebrews, has e  met with us; and now, please let us go a three daysjourney into the wilderness, that we may sacrifice to the  Lord our God.’
Copyright information for ESV