The Lord appeared to Abraham by the oaks of Mamre, as he sat at the entrance of his tent in the heat of the day. - Genesis 18:1
This is another beginning for Abraham. He'd undergone one when he listened to God and left Ur for some undisclosed land of promise. Just uprooted his family and moved on. That took faith (although some would attribute it to something else). They had found their promised land and settled down but Lot, Abraham's nephew wasn't happy. He moved on to the big city -- well, a place with a lot more excitement and activity than a bunch of tents out in the middle of a few hundred square miles of pasture and desert. That left Abraham the master of all he surveyed, and the front of the tent was as good a place as any to contemplate. Little did he know that that was the start of a new chapter in his life -- and that of the wole world.
Abraham was counted as righteous. So he lied a couple of times about his wife being his sister. It really wasn't a lie because Sarah was really his half sister, but that kind of thing went on all the time back then. He was a good guy. He gave Lot his choice of where to live when the tent area got too small for the both of them. When he saw three strangers approaching he did the exact proper thing for a nomadic tent dweller in that time when Holiday Inn or McDonalds hadn't been invented, he went out to greet them, welcome them, get the staff (including his wife) to prepare a meal and then act the perfect host. It would be a life-changing welcome.
What can I learn from Abraham? It never hurts to be generous and hospitable to strangers as much as to expected guests or family members. You never know who's going to come knocking.
Welcome strangers lavishly.