Vayerà

G‑d paid Abraham a visit, as he sat at the entrance of his tent. Abraham suddenly noticed three travelers passing by, and ran to invite them into his home. These passersby, who were actually angels in human disguise, accepted the invitation, and Abraham and Sarah prepared a sumptuous feast for them. The angels informed Abraham that Sarah would give birth to a child exactly one year later. Eighty-nine-year-old, post-menopausal Sarah, who was standing nearby, heard this assurance, and laughed. G‑d was displeased with Sarah's lack of faith.

Abraham's tents by Michael Muchnik

G.d appeared to Abraham at the Oaks of Mamre while he was sitting at the entrance of his tent. It was the hottest part of the day. 

 THE OAK OF MAMRE

Oval wooden hand-painted with the children showing the oak of Mamre, and the three angels

Lech Lecha

And the Lord said to Abram, "Go forth from your land and from your birthplace and from your father's house, to the land that I will show you. I will make you into a great nation, and I will bless you, and I will aggrandize your name, and [you shall] be a blessing. And I will bless those who bless you, and the one who curses you I will curse, and all the families of the earth shall be blessed in you." (bereshit 12:1-3)
And G-d took him outside, and said, "Please look heavenward and count the stars, if you are able to count them." And He said to him, "So will be your offspring.." And he believed in the Lord, and He accounted it to him as righteousness.(Bereshit 15:5-6)

Glittering stars waterglobe 

 Glass jar outside painted with stars and filled with glitter, water and glycerin