Then Samuel took the horn of oil, and anointed him in the midst of his brethren: and the Spirit of the LORD came upon David from that day forward. So Samuel rose up, and went to Ramah.
Then Samuel took the horn of oil, and anointed him. This transaction must have been strictly private, according to Josephus, who states that Samuel whispered the object of it in his ear. But the sacred historian says expressly that it was done "in the midst of his brethren." Whether the elders of Beth-lehem were present or not, Jesse and all his sons were witnesses of the ceremony, and cognizant of its import, (see the notes at the end of 1 Samuel 17:1-58.)
And the Spirit of the Lord came upon David from that day forward - (see the note at 1 Samuel 10:1.) 'The anointing is placed in causal connection with the communication of the Spirit, the former typifying what the latter secured (cf. Mark 6:13; James 5:14): it was a seal and pledge of the blessings which the Lord bestowed upon the rulers of the nation for the people's good' (Hengstenberg, 'Christology,' 3:, p. 125).