The Prophet ﷺ interlaced his fingers.
شبك النبي ﷺ أصابعه.
No references are available.
Bukhari narrated it in the Book of Prayer (478, 479) from Hamid bin Umar, from Bishr, who said, Aasim narrated to us, who said, Waqid narrated to us, from his father, from Ibn Umar, who said... and he mentioned it.