What is the implication of "ve'ha'Levi Lo Sa'azvenu"?
Rashi: It implies a La'av for failing to give the Levi Ma'aser Rishon..
Rashbam: Rather, let him rejoice together with you and it will be good for you and for him.
Sifri: 'If one doesn't have Ma'aser Rishon to give him, one should give him Ma'aser Sheini Ma'aser Ani or Shelamim, and if one doesn't have Shelamim either, one should give him Tzedakah. 1
See Torah Temimah, note 77.
Why does the Torah add "Ki Ein lo Cheilek ve'Nachalah Imach"?
Rashi: To exempt Hefker, Leket, Shikchah and Pe'ah - in which a Levi has equal rights to a Yisrael - from Ma'aser Rishon.
Oznayim la'Torah: With reference to the previous Pesukim - Do not forsake him, since he has no inheritance from which to separate Ma'aser Sheini to take to Yerushalayim 1 .
See Torah Temimah citing the Sifri and note 77.
QUESTIONS ON RASHI
Rashi writes that "Lo Sa'azvenu" is only if he does not give him Ma'aser. But earlier - in 12:18 - he said that one who does not have Ma'aser must feed the Levi from his own food?
Refer to 12:19:152:1 & 2,


