I have never seen Messenger of Allah, ﷺ but observing the prayers at their appointed times except two prayers, sunset and 'Isha, ' at Muzdalifa (where he deferred the sunset prayer to combine it with 'Isha' and he observed the dawn prayer before its stipulated time on that day (10th of Dhu'l-Hijja).  

مَا رَأَيْتُ رَسُولَ اللَّهِ ﷺ صَلَّى صَلاَةً إِلاَّ لِمِيقَاتِهَا إِلاَّ صَلاَتَيْنِ صَلاَةَ الْمَغْرِبِ وَالْعِشَاءِ بِجَمْعٍ وَصَلَّى الْفَجْرَ يَوْمَئِذٍ قَبْلَ مِيقَاتِهَا  

This hadith has been transmitted by Al-Aʿmash with a slight variation of words, i.e. he said before its time when it was still dark.  

وَقَالَ قَبْلَ وَقْتِهَا بِغَلَسٍ