Sforno on Genesis 35:1/ספורנו על בראשית ל״ה:א׳

1ושב שם. An invitation to prepare himself mentally and spiritually before beginning to build the altar that he had in mind to erect. This corresponds to what our sages have described as being the manner in which they prepared for prayer and subsequently unwound before pursuing mundane activities. According to Berachot 30 they spent an hour “gearing up” before commencing their prayers and then spent an hour unwinding before going about the business of earning their daily bread.

2ועשה שם מזבח לא-ל הנראה אליך בברחך, in order to give thanks to G’d Who has kept His promise which He gave you on that occasion. We have a long standing tradition that when one passes a location where one had once experienced G’d’s help in a clearly supernatural format one is to recite a special benediction giving thanks to G’d for having done so, even though the event may have taken place a long time ago. (Berachot 54).