Samuel said, How can I go? if Saul hear it, he will kill me. Yahweh said, Take a heifer with you, and say, I am come to sacrifice to Yahweh.
Now that shows you how far Saul has strayed from the Lord, and the things of the Lord, he would actually kill the prophet of God. Samuel realized this, "This guy is really gone off the deep end. Lord if he hears I'm going to go down and anoint another king, he's gonna kill me."