'Obey My Voice' in the Bible

Then he wrote another letter to them saying, "If ye be mine and will obey my voice, then take the heads of your master's sons and come to me to Jezreel, by tomorrow this time." And the king's sons were seventy persons with the great men of the city which nourished them.

but this I commanded them, saying, 'Hearken and obey my voice, and I shall be your God, and ye shall be my people: so that ye walk in all the ways, which I have commanded you, that ye may prosper.'