1)
What is the meaning of "va'Ya'as Hashem Lo"?
1.
Radak citing Targum Yonasan: He will do to David.
2.
Radak: "Lo" is like Lecha (to you). Verses often speak in second person and third person within one matter.
3.
Malbim: Hashem informs of Divine decrees so the people will repent, and will know for what sin it came. (a) He did not answer you, for Teshuvah will not nullify the decree, for He already promised the kingship to David. (b) You already know for what sin it came (Amalek, verse 18).
2)
Why did Shmuel tell Sha'ul only now that David will take his kingship?
1.
Rashi citing Midrash Shmuel 24:6: In his lifetime, he feared lest Sha'ul kill him, for he anointed David.
