'What Happens When a Shia Stands Up For Prayer?'

Imam Al-Baqir (as) said,

"Whenever any of our followers stands up to pray, angels whose number equal our enemie's numbers shall stand to pray behind him, and they will pray for him until he finishes praying."

[Mishkat Ul-Anwar Pg 206]

(Jama'at Namaz in the Holy Shrine of Abu Fadhel Abbas)