1)
From what will you save yourself?
1.
Rashi: You will save yourself from feuds after David dies. Your son will want to rule, like Hashem promised!
2.
Radak #1, Malbim (11): You will save your lives - after Adoniyahu is king, he will kill you and Shlomo, lest there be a challenge to his kingship!
3.
Radak #2: You will save yourself and your son from shame, of being slaves to Adoniyahu.
