ENOfficial
'Amr ibn Shu'aib reports on the authority of his father that his grandfather said: "I saw Allah's Messenger (Allah bless him and give him peace) drink while both standing and sitting.”
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ: حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، عَنْ حُسَيْنٍ الْمُعَلِّمِ، عَنْ عَمْرِو بْنِ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، قَالَ: رَأَيْتُ رَسُولَ اللهِ صلى الله عليه وسلم، يَشْرَبُ قَائِمًا، وَقَاعِدًا.
sunnah.com