كتاب الصلاة
2  
The Book of Prayer
Bulugh al-Maram 238
Narrated Abu Hurairah (RA):
Allah's Messenger (ﷺ) forbade keeping one's hands on one's waist while praying. [Agreed upon]. The wording is that of Muslim's.

And it's meaning is to put (one's) hands on his waist.

عَنْ أَبِي هُرَيْرَةَ ‏- رضى الله عنه ‏- قَالَ : { نَهَى رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-أَنْ يُصَلِّيَ اَلرَّجُلُ مُخْتَصِرًا } مُتَّفَقٌ عَلَيْهِ , وَاللَّفْظُ لِمُسْلِمٍ .‏ 1

وَمَعْنَاهُ : أَنْ يَجْعَلَ يَدَهُ عَلَى خَاصِرَتِهِ 2
Reference : Bulugh al-Maram 238
In-book reference : Book 2, Hadith 238
English translation : Book 2, Hadith 236
Hadith Text
Reference