'Abdullah bin Mas'ud Radiyallahu 'Anhu reports:
"Once at night I performed salaah with Rasulullah Sallallahu 'Alayhi Wasallam. Rasulullah Sallallahu 'Alayhi Wasallam stood for such a long time that I intended to commit an evil deed". Someone asked him what deed did you intend to commit? He replied. "To sit down and leave Rasulullah Sallallahu 'Alayhi Wasallam alone".
English reference: Book 39, Hadith 262
Arabic reference: Book 40, Hadith 277