As told by
re: following verse (Gen. 28:16)
ואנוכי לא ידעתי
After Yakov had laid down to sleep at Har Hamoriah, the verse reads:
"וייקץ יעקוב משנתו ויאמר"
- the last letters of which spell
So we can understand the verse to mean this:
"That if a person prays in a minyan (צבור), then he can be certain that - as the verse continues:
"יש ה׳ במקום הזה"
and his prayers are accepted.
However, should he pray by himself - as the verse continues:
then the acceptance of his prayers are now more in doubt - as the verse continues: