Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) came at the time of Fajr, and some people had leaned their backs against the qiblah, so he said: "Move back from the qiblah; do not come between the angels and the qiblah, for this is the prayer of the angels."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8913