Why does it say "Milvad"?
Radak: They gave to Kohanim in their cities, aside from what they gave to them when they came to Beis Hashem.
Malbim: These two verses (16-17) are like a Ma'amar Musgar (parenthetical comment). Korei and those appointed with him (14-15), they were only to give to Kohanim and Leviyim in their cities. Here teaches that those who came for Avodah did not receive from them, rather, via Kananyah and Shim'i (12-13).
What is the meaning of "Hisyachsam"?
Radak: Fathers will come with their sons.
Malbim: Yichus (lineage) applies also below (sons), like here, and also above (fathers, in the coming verse).
What is the significance of three years and above?
Redak #1: It is improper to bring males to Beis Hashem below three years. Females did not come, above or below three.
Radak #2: Below three years, he lacks Da'as to guard what is in his hand. One does not give to him Terumah, lest he be Metamei it 1 . Such children often touch dead Sheratzim. Above three years, he knows to guard his hands after they train him.
Malbim: From three and above, they come to learn from their father. Even though they are not proper for Avodah, they received portions with their father.
We do not give Terumah to a minor (less than 13) at the granary, but we send it to his house (Yevamos 99b). R. Chananel explains that we are concerned lest he be Metamei it; most explain that it is due to disgrace. They could agree that below three, we are also concerned for Tum'ah. (PF)
What do we learn from "b'Mishmerosam k'Machlekoseihem"?
Malbim: Each Mishmar that served received its portion via Kananyah, who was appointed in Yerushalayim.
