1)
To which Avos does this refer?
1.
Rashi: Those in Egypt and in the Midbar.
2.
Radak: It is Dor ha'Midbar, who did not put their trust in Him, and did not prepare their hearts to Him.
3.
Malbim: They were rebellious - they knew their Master and rebelled against Him.
2)
What is the meaning of "v'Lo Ne'emnah Es Kel Rucho"?
1.
Radak #1: They did not fulfill with Kel His Nefesh, intent and desire. This is like "u'Skativ Yased b'Makom Ne'eman" (Yeshayah 22:23), i.e. lasting.
2.
Radak #2: "Ne'emnah" is simply an expression of Emunah.
3.
Malbim: The inner Ru'ach that puts pictures on the heart, it put evil pictures of every sin, to the point that he could not stand in Emunah in Hashem's Avodah.
