There are 3 religions that says so. The obvious one is Christianity with that being it's central term. The second one is Hindu. Khrisna is said to be a God incarnate.

But in torah I often see stories about Abraham meeting some guys and recognize that the guy is G_d himself.

Genesis 18 for example says
And Jehovah appeareth unto him among the oaks of Mamre, and he is sitting at the opening of the tent, about the heat of the day; 2 and he lifteth up his eyes and looketh, and lo, three men standing by him, and he seeth, and runneth to meet them from the opening of the tent, and boweth himself towards the earth, 3 And he saith, 'My Lord, if, I pray thee, I have found grace in thine eyes, do not, I pray thee, pass on from thy servant

http://yltbible.com/genesis/18.htm

So here Jehovah (=God?) appear unto him among the oaks and sit. So who is this Jehovah that sit at the opening of the tent? I thought God never incarnate? How can he sit at the opening of the tent?


Also we have Jacob wrestle with G_d with G_d's performance not being very impressive. G_d can't escape Jacob's hold. 

So do jews believe that G_d, once in a while, take humans' form?