What is the meaning of "Putzu"?
Rashi: Announce in many place. The announcers will be Nefutzim (scattered among the people).
What is the meaning of "u'Shchatetem ba'Zeh"?
Rashi #1: You will slaughter here. Malbim - close to the Mizbe'ach, so you can throw the blood immediately.
Rashi #2 (from Chulin 17b): He checked a knife 1 for them. Chomas Anach - ba'Zeh is the acronym of b'Sachin Zeh ha'Baduk (with this checked knife).
Radak (citing Vayikra Rabah 25:8): He showed them a knife [whose blade was] 14 (the Gematriya of ba'Zeh) fingers long. 2
Chulin 17b: This is an Asmachta (support) for the law that one must check a Shechitah knife [to ensure that it is smooth].
Chulin 2:3: If one moves the knife back and forth, it may be short. If he slaughters in one motion, its length must be at least twice the width of the animal's neck. Rema (YD 8:1) - our verse hints that this is 14 fingers.
Why did he say "at night"?
Rashi: Refer to 14:33:4:1,2.
What is "El ha'Dam"?
Radak: It is like Al ha'Dam. This is like "El he'Harim Lo Achal" (Yechezkel 18:6) - it is like Al he'Harim.
