بُلُوغُ الْمَرَامِ
Bulugh al-Maram 291
The Book of Prayer
وَلِلطَّبَرَانِيِّ مِنْ حَدِيثِ اِبْنِ مَسْعُودٍ : { يُدِيمُ ذَلِكَ } [1]
at-Tabarani narrated the Hadith of Ibn Mas'ud which has the addition "... he [the Prophet (ﷺ)] did that constantly."
Sunnah.com reference: Book 2, Hadith 177