Muwatta Malik 110
Purity
حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ إِسْمَاعِيلَ بْنِ أَبِي حَكِيمٍ، أَنَّ عَطَاءَ بْنَ يَسَارٍ، أَخْبَرَهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَبَّرَ فِي صَلاَةٍ مِنَ الصَّلَوَاتِ ثُمَّ أَشَارَ إِلَيْهِمْ بِيَدِهِ أَنِ امْكُثُوا فَذَهَبَ ثُمَّ رَجَعَ وَعَلَى جِلْدِهِ أَثَرُ الْمَاءِ .
Yahya related to me from Malik from Ismail ibn Abi Hakim that Ata ibn Yasar told him that the Messenger of Allah, may Allah bless him and grant him peace, said the takbir in one of the prayers and then indicated to them with his hand to stay in place. He left and then returned with traces of water on his skin
Grading: Salim al-Hilali: Sahih Lighairihi
Text from the public-domain hadith-api dataset. Numbering follows that dataset and can differ by a few from some printed editions — check the wording, not only the number.