Why did they find it necessary to permit them to trade in Shechem?
Seforno: Because only the residents were permitted to trade freely; strangers might be required to obtain express permission to do so. 1
Malbim: There were six things that normally, strangers are not entitled to, and you will attain (through joining us). (a) They cannot intermarry with the residents; now - "your daughters you will give to us." (b) They cannot live in the market and the choice places in the city; now - "you will live with us." (c) They cannot use public places; now - "the land will be in front of you." (d) They cannot stay a long time - but now, "Shevu." (e) They cannot do business like they want; now - "u'Secharuha." (f) They cannot buy a field for an Achuzah (for all generations); but now - "v'He'achazu Bah."
Ha'amek Davar: You may buy grain here and sell it elsewhere, or buy from elsewhere and sell to individuals here.
As the Gemara explains in Bava Basra (21b).
Why did he say "v'Itanu Teshevu"?
Ha'amek Davar: You will not be so distinct and distanced from us.
