Yahweh said to Samuel, How long will you mourn for Saul, seeing I have rejected him from being king over Israel? fill your horn with oil, and go: I will send you to Jesse the Bethlehemite; for I have provided me a king among his sons.
"Take a heifer with you, and say, I am come to sacrifice to the Lord"  (1 Samuel 16:2) This was God's requirement that the mission be conducted secretly.  This was neither duplicity nor falsehood, but discretion and concealment, both of which are honorable.