¹And the LORD appeared unto him in the plains of Mamre: and he sat in the tent door in the heat of the day;

 ²And he lift up his eyes and looked, and, lo, three men stood by him: and when he saw them, he ran to meet them from the tent door, and bowed himself toward the ground,

 ³And said, My LORD, if now I have found favour in thy sight, pass not away, I pray thee, from thy servant:

 ⁴Let a little water, I pray you, be fetched, and wash your feet, and rest yourselves under the tree:

 ⁵And I will fetch a morsel of bread, and comfort ye your hearts; after that ye shall pass on: for therefore are ye come to your servant. And they said, So do, as thou hast said.

 ⁶And Abraham hastened into the tent unto Sarah, and said, Make ready quickly three measures of fine meal, knead it, and make cakes upon the hearth.

 ⁷And Abraham ran unto the herd, and fetcht a calf tender and good, and gave it unto a young man; and he hasted to dress it.

 ⁸And he took butter, and milk, and the calf which he had dressed, and set it before them; and he stood by them under the tree, and they did eat.

 ⁹And they said unto him, Where is Sarah thy wife? And he said, Behold, in the tent.

 ¹⁰And he said, I will certainly return unto thee according to the time of life; and, lo, Sarah thy wife shall have a son. And Sarah heard it in the tent door, which was behind him.

 ¹¹Now Abraham and Sarah were old and well stricken in age; and it ceased to be with Sarah after the manner of women.

 ¹²Therefore Sarah laughed within herself, saying, After I am waxed old shall I have pleasure, my lord being old also?

 ¹³And the LORD said unto Abraham, Wherefore did Sarah laugh, saying, Shall I of a surety bear a child, which am old?

 ¹⁴Is any thing too hard for the LORD? At the time appointed I will return unto thee, according to the time of life, and Sarah shall have a son.

 ¹⁵Then Sarah denied, saying, I laughed not; for she was afraid. And he said, Nay; but thou didst laugh.

 ¹⁶And the men rose up from thence, and looked toward Sodom: and Abraham went with them to bring them on the way.

 ¹⁷And the LORD said, Shall I hide from Abraham that thing which I do;

 ¹⁸Seeing that Abraham shall surely become a great and mighty nation, and all the nations of the earth shall be blessed in him?

 ¹⁹For I know him, that he will command his children and his household after him, and they shall keep the way of the LORD, to do justice and judgment; that the LORD may bring upon Abraham that which he hath spoken of him.

 ²⁰And the LORD said, Because the cry of Sodom and Gomorrah is great, and because their sin is very grievous;

 ²¹I will go down now, and see whether they have done altogether according to the cry of it, which is come unto me; and if not, I will know.

 ²²And the men turned their faces from thence, and went toward Sodom: but Abraham stood yet before the LORD.

 ²³And Abraham drew near, and said, Wilt thou also destroy the righteous with the wicked?

 ²⁴Peradventure there be fifty righteous within the city: wilt thou also destroy and not spare the place for the fifty righteous that are therein?

 ²⁵That be far from thee to do after this manner, to slay the righteous with the wicked: and that the righteous should be as the wicked, that be far from thee: Shall not the Judge of all the earth do right?

 ²⁶And the LORD said, If I find in Sodom fifty righteous within the city, then I will spare all the place for their sakes.

 ²⁷And Abraham answered and said, Behold now, I have taken upon me to speak unto the LORD, which am but dust and ashes:

 ²⁸Peradventure there shall lack five of the fifty righteous: wilt thou destroy all the city for lack of five? And he said, If I find there forty and five, I will not destroy it.

 ²⁹And he spake unto him yet again, and said, Peradventure there shall be forty found there. And he said, I will not do it for forty's sake.

 ³⁰And he said unto him, Oh let not the LORD be angry, and I will speak: Peradventure there shall thirty be found there. And he said, I will not do it, if I find thirty there.

 ³¹And he said, Behold now, I have taken upon me to speak unto the LORD: Peradventure there shall be twenty found there. And he said, I will not destroy it for twenty's sake.

 ³²And he said, Oh let not the LORD be angry, and I will speak yet but this once: Peradventure ten shall be found there. And he said, I will not destroy it for ten's sake.

 ³³And the LORD went his way, as soon as he had left communing with Abraham: and Abraham returned unto his place.

Here is the excellent JFB commentary on this passage:

CHAPTER 18

Ge 18:1-8. Entertainment of Angels.

1. the Lord appeared—another manifestation of the divine presence, more familiar than any yet narrated; and more like that in the fulness of time, when the Word was made flesh.

plains of Mamre—rather, terebinth or oak of Mamre; a tall-spreading tree or grove of trees.

sat in the tent door—The tent itself being too close and sultry at noon, the shaded open front is usually resorted to for the air that may be stirring.

2. lift up his eyes … and, lo, three men—Travellers in that quarter start at sunrise and continue till midday when they look out for some resting-place.

he ran to meet them—When the visitor is an ordinary person, the host merely rises; but if of superior rank, the custom is to advance a little towards the stranger, and after a very low bow, turn and lead him to the tent, putting an arm round his waist, or tapping him on the shoulder as they go, to assure him of welcome.

3. My Lord, if now I have found favor—The hospitalities offered are just of the kind that are necessary and most grateful, the refreshment of water, for feet exposed to dust and heat by the sandals, being still the first observed among the pastoral people of Hebron.

5. for therefore are ye come—No questions were asked. But Abraham knew their object by the course they took—approaching directly in front of the chief sheik's tent, which is always distinguishable from the rest and thus showing their wish to be his guests.

6. Abraham hastened … unto Sarah … make cakes upon the hearth—Bread is baked daily, no more than is required for family use, and always by the women, commonly the wife. It is a short process. Flour mixed with water is made into dough, and being rolled out into cakes, it is placed on the earthen floor, previously heated by a fire. The fire being removed, the cakes are laid on the ground, and being covered over with hot embers, are soon baked, and eaten the moment they are taken off.

7. Abraham ran unto the herd, and fetched a calf—Animal food is never provided, except for visitors of a superior rank when a kid or lamb is killed. A calf is still a higher stretch of hospitality, and it would probably be cooked as is usually done when haste is required—either by roasting it whole or by cutting it up into small pieces and broiling them on skewers over the fire. It is always eaten along with boiled corn swimming in butter or melted fat, into which every morsel of meat, laid upon a piece of bread, is dipped, before being conveyed by the fingers to the mouth.

8. milk—A bowl of camel's milk ends the repast.

he stood by them under the tree—The host himself, even though he has a number of servants, deems it a necessary act of politeness to stand while his guests are at their food, and Abraham evidently did this before he was aware of the real character of his visitors.

Ge 18:9-15. Reproof of Sarah. An inquiry about his wife, so surprising in strangers, the subject of conversation, and the fulfilment of the fondly cherished promise within a specified time, showed Abraham that he had been entertaining more than ordinary travellers (Heb 13:2).

10. Sarah heard it in the tent door, which was behind him—The women's apartment is in the back of the tent, divided by a thin partition from the men's.

12. Therefore Sarah laughed within herself—Long delay seems to have weakened faith. Sarah treated the announcement as incredible, and when taxed with the silent sneer, she added falsehood to distrust. It was an aggravated offense (Ac 5:4), and nothing but grace saved her (Ro 9:18).

Ge 18:16-22. Disclosure of Sodom's Doom.

16. the men rose … Abraham went with them—It is customary for a host to escort his guests a little way.

17. the Lord said, Shall I hide—The chief stranger, no other than the Lord, disclosed to Abraham the awful doom about to be inflicted on Sodom and the cities of the plain for their enormous wickedness.

21. I will go down … and see—language used after the manner of men. These cities were to be made examples to all future ages of God's severity; and therefore ample proof given that the judgment was neither rash nor excessive (Eze 18:23; Jer 18:7).

Ge 18:23-33. Abraham's Intercession.

23. Abraham drew near, and said,&c.—The scene described is full of interest and instruction—showing in an unmistakable manner the efficacy of prayer and intercession. (See also Pr 15:8; Jas 5:16). Abraham reasoned justly as to the rectitude of the divine procedure (Ro 3:5, 6), and many guilty cities and nations have been spared on account of God's people (Mt 5:13; 24:22).

33. the Lord … left communing … and Abraham returned unto his place—Why did Abraham cease to carry his intercessions farther? Either because he fondly thought that he was now sure of the cities being preserved (Lu 13:9), or because the Lord restrained his mind from further intercession (Jer 7:16; 11:14). But there were not ten "righteous persons." There was only one, and he might without injustice have perished in the general overthrow (Ec 9:2). But a difference is sometimes made, and on this occasion the grace of God was manifested in a signal manner for the sake of Abraham. What a blessing to be connected with a saint of God!