What is "Er v'Oneh"?
Rashi citing Sanhedrin 82a: If he is a Chacham, he will not have a son that is Er (sharp) among Chachamim and can Oneh (answer) Talmidim 1 . If he is a Kohen, he will not have a son that brings Menachos (i.e. does Avodah).
Radak: It is someone alive in his house who can answer one who calls. Er is the opposite of dead, who sleeps - "Pen Ishan ha'Maves" (Tehilim 13:4), "Yashanti Az Yanu'ach Li" (Iyov 3:13).
Radak citing Targum Yonasan: A son and a grandson.
Malbim: Er is awake from sleep. All will sleep forever (die). Will not be found even Oneh - one who dozes, and can answer if they call to him and arouse him from his sleep.
Malbim: This is sleep of the intellect Nefesh. The intellect of Chachamim is totally awake. The children will follow their Nochris mothers, and have no share in Torah or Avodah.
What is "Magish Minchah"?
Rashi: Refer to 2:12:1:1.
