God said that he wouldn't let anyone in Saul's family ever be king again and that David would be king instead. He also said that David would rule both Israel and Judah, all the way from Dan in the north to Beersheba in the south.
Samuel poured the oil on David's head while his brothers watched. At that moment, the Spirit of the LORD took control of David and stayed with him from then on. Samuel returned home to Ramah.