There is nothing in old covenant law that prohibits believers from visiting Gentiles or eating with them. Old covenant law restricts the food that may be eaten but not the company. No doubt there were additional expectations alongside these laws which meant that Jews generally considered it to be inappropriate to eat with Gentiles and/or visit in their homes as a result of their being a potential source of ritual defilement.1 These are likely the laws/traditions which Peter has in mind.2
28 Vous savez, leur dit-il, qu'il est défendu à un Juif de se lier avec un étranger ou d'entrer chez lui; mais Dieu m'a appris à ne regarder aucun homme comme souillé et impur.