Who were the giants?

And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them,  That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose.  And the LORD said, My spirit shall not always strive with man, for that he also is flesh: yet his days shall be an hundred and twenty years.  There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown.  And GOD saw that the wickedness of man was great in the earth, and that every imagination of the thoughts of his heart was only evil continually.  

Genesis 6:1-5

And Caleb stilled the people before Moses, and said, Let us go up at once, and possess it; for we are well able to overcome it.  But the men that went up with him said, We be not able to go up against the people; for they are stronger than we.  And they brought up an evil report of the land which they had searched unto the children of Israel, saying, The land, through which we have gone to search it, is a land that eateth up the inhabitants thereof; and all the people that we saw in it are men of a great stature.  And there we saw the giants, the sons of Anak, which come of the giants: and we were in our own sight as grasshoppers, and so we were in their sight.  

Numbers 13:30-33

All the cities of the plain, and all Gilead, and all Bashan, unto Salchah and Edrei, cities of the kingdom of Og in Bashan.  For only Og king of Bashan remained of the remnant of giants; behold, his bedstead was a bedstead of iron; is it not in Rabbath of the children of Ammon? nine cubits was the length thereof, and four cubits the breadth of it, after the cubit of a man.  And this land, which we possessed at that time, from Aroer, which is by the river Arnon, and half mount Gilead, and the cities thereof, gave I unto the Reubenites and to the Gadites.  And the rest of Gilead, and all Bashan, being the kingdom of Og, gave I unto the half tribe of Manasseh; all the region of Argob, with all Bashan, which was called the land of giants.  

Deuteronomy 3:10-13

And it came to pass after this, that there arose war at Gezer with the Philistines; at which time Sibbechai the Hushathite slew Sippai, that was of the children of the giant: and they were subdued.  And there was war again with the Philistines; and Elhanan the son of Jair slew Lahmi the brother of Goliath the Gittite, whose spear staff was like a weaver's beam.  And yet again there was war at Gath, where was a man of great stature, whose fingers and toes were four and twenty, six on each hand, and six on each foot: and he also was the son of the giant.  But when he defied Israel, Jonathan the son of Shimea David's brother slew him.  These were born unto the giant in Gath; and they fell by the hand of David, and by the hand of his servants.  

1 Chronicles 20:4-8

And there went out a champion out of the camp of the Philistines, named Goliath, of Gath, whose height was six cubits and a span.  And he had an helmet of brass upon his head, and he was armed with a coat of mail; and the weight of the coat was five thousand shekels of brass.  And he had greaves of brass upon his legs, and a target of brass between his shoulders.  And the staff of his spear was like a weaver's beam; and his spear's head weighed six hundred shekels of iron: and one bearing a shield went before him.  

1 Samuel 17:4-7

Moreover the Philistines had yet war again with Israel; and David went down, and his servants with him, and fought against the Philistines: and David waxed faint.  And Ishbi–benob, which was of the sons of the giant, the weight of whose spear weighed three hundred shekels of brass in weight, he being girded with a new sword, thought to have slain David.  But Abishai the son of Zeruiah succoured him, and smote the Philistine, and killed him. Then the men of David sware unto him, saying, Thou shalt go no more out with us to battle, that thou quench not the light of Israel.  And it came to pass after this, that there was again a battle with the Philistines at Gob: then Sibbechai the Hushathite slew Saph, which was of the sons of the giant.  And there was again a battle in Gob with the Philistines, where Elhanan the son of Jaare–oregim, a Beth–lehemite, slew the brother of Goliath the Gittite, the staff of whose spear was like a weaver's beam.  And there was yet a battle in Gath, where was a man of great stature, that had on every hand six fingers, and on every foot six toes, four and twenty in number; and he also was born to the giant.  And when he defied Israel, Jonathan the son of Shimea the brother of David slew him.  These four were born to the giant in Gath, and fell by the hand of David, and by the hand of his servants.  

2 Samuel 21:15-22

That the LORD spake unto me, saying,  Thou art to pass over through Ar, the coast of Moab, this day:  And when thou comest nigh over against the children of Ammon, distress them not, nor meddle with them: for I will not give thee of the land of the children of Ammon any possession; because I have given it unto the children of Lot for a possession.  (That also was accounted a land of giants: giants dwelt therein in old time; and the Ammonites call them Zamzummims;  A people great, and many, and tall, as the Anakims; but the LORD destroyed them before them; and they succeeded them, and dwelt in their stead:  

Deuteronomy 2:17-21

And at that time came Joshua, and cut off the Anakims from the mountains, from Hebron, from Debir, from Anab, and from all the mountains of Judah, and from all the mountains of Israel: Joshua destroyed them utterly with their cities.  There was none of the Anakims left in the land of the children of Israel: only in Gaza, in Gath, and in Ashdod, there remained.  

Joshua 11:21-22

Now therefore give me this mountain, whereof the LORD spake in that day; for thou heardest in that day how the Anakims were there, and that the cities were great and fenced: if so be the LORD will be with me, then I shall be able to drive them out, as the LORD said.  And Joshua blessed him, and gave unto Caleb the son of Jephunneh Hebron for an inheritance.  Hebron therefore became the inheritance of Caleb the son of Jephunneh the Kenezite unto this day, because that he wholly followed the LORD God of Israel.  And the name of Hebron before was Kirjath–arba; which Arba was a great man among the Anakims. And the land had rest from war.  

Joshua 14:12-15

Now there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them.  

Job 1:6

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