|The innocent seldom find an uncomfortable pillow. - Cowper|
So what do you know about stone pillows?
28:10-11 Now Jacob went out from Beersheba and went toward Haran. So he came to a certain place and stayed there all night, because the sun had set. And he took one of the stones of that place and put it at his head, and he lay down in that place to sleep.
One of my study bibles says he may have used the stone to protect his head, rather than as a pillow. Concealment, maybe? This must have made sense to the original readers of the story but I don't understand what he did with this rock while he was sleeping.As you have doubtless noticed, a number of commentators claim that he literally used the rock as a pillow.* But the word itself apparently means "headplace" (Keil and Delitzsch) or "headpiece" (Strongs). It can, but does not necessarily, mean "pillow." In short, it's something he put at his head while he slept and the rest is context. That he put it under his head I doubt – the dude had lots of sheep, so I'm sure he owned a very nice sheepskin pillow.
Though the text does not mention others with Jacob, it was also highly unlikely he was traveling alone through such dangerous country; most likely he had an impressive retinue of guards and servants.** These would not only serve to deter raiders, but would also impress his future wife and perhaps more importantly, her father. It's rather like Abraham earlier in the text – from reading Genesis it's easy to presume he lives alone with Sarah; then suddenly he raises an army of more than 300 men (14:14) who just happen to live in his "household." We're dealing with the tribal described as personal, and the actions of a group epitomized by its chief. So it might have been a very large stone that protected not only him, but many men.
It seems to me that there is something symbolically honorable or at least meaningful about the stone being at his head, though I have no idea exactly what it is, nor, judging from the mass of contradictory commentary concerning it, does anyone else. Perhaps it was a particularly attractive or unusual stone, but I highly doubt that its main quality was that it made a fine pillow.*** For whatever reason, Jacob concluded that this stone, of the many around, would make a fitting monument to his fathers' God; the qualities that made it a good monument probably account for him placing it as a "headplace" in the first place.
But the fact that he placed this stone at his head before he had the vision is explanatory to the original audience, who would have understood that it was a special rock that he used to make a meaningful monument to God.
That's my vague and wholly unsupported opinion, and worth what it cost you.
* The KJV, in v. 18, incongruously mentions "the stone that he had put for his pillows."
** I'm sure he could have borrowed a pillow from one of them and not slept on a rock.
*** That's not the sort of quality that makes a fitting monument to any god but Hypnos.