1)
Why did they bless that his house be like Beis Peretz?
1.
Rashi: We 1 come from Peretz.
2.
Malbim: Bnei Yevamah are called on the name of the Mes. Also Peretz came from Tamar, which was like a matter of Yibum. Peretz is attributed to Yehudah, and all honor of his father's house is attributed to him. So will be the house that will come from this girl.
3.
Refer to 4:11:1:2.
1
I.e. most of the people there, who were from Beis Lechem. (PF)