3,467. Leniencies for Travelers

Hilchos Maaser 12:8

The previous halacha applies when the traveler doesn’t know anyone in his new location. However, if he knows people there, he may only buy from someone known to be reliable. If he remains in that location for thirty days, he may only buy produce from someone proficient in tithes. This is so even if he still doesn’t know anyone there.

Hilchos Maaser 12:9

The aforementioned leniencies only apply to terumos and maaseros; when it comes to matters of Sabbatical-year produce and ritual purity, one may only buy from someone proficient is such things.