Rashi: My great ones. Every Meshichah is an expression of authority and grandeur.
2.
Radak: They are nobles. They were honored among kings, as if they were anointed kings. Bnei Ches told Avraham "Nesi Elokim Atah b'Sochenu" (Bereishis 23:6), and Avimelech went after Yitzchak to make Shalom with him.
I.e. Hashem did not let Avimelech touch Sarah. (PF)
2)
How did Hashem tell them not to touch "Meshichai"?
1.
Radak: He warned Avimelech and Lavan in dreams, and sent plagues against Pharaoh and Avimelech. 'Rashi' (Divrei ha'Yamim I, 16:22) - also, when Kena'anim wanted to kill Yakov because [his sons] wiped out Shechem, [they did not, for] "fear of Elokim" (Bereishis 35:5) was on them.
2.
Malbim: All this is "Davar Tzivah l'Elef Dor" (verse 8).
3)
Who are "Nevi'ai"?
1.
Radak: The Avos; they were Nevi'im. Hashem spoke to them in prophecy and in dreams. It says about Avraham "Hashev Eshes ha'Ish Ki Navi Hu" (Bereishis 20:7).
