Muwatta Malik 184

وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ عَبْدَ اللَّهِ بْنَ عُمَرَ، كَانَ يَقْرَأُ فِي الصُّبْحِ فِي السَّفَرِ بِالْعَشْرِ السُّوَرِ الأُوَلِ مِنَ الْمُفَصَّلِ فِي كُلِّ رَكْعَةٍ بِأُمِّ الْقُرْآنِ وَسُورَةٍ ‏.‏

Yahya related to me from Malik from Nafi that Abdullah ibn Umar used to recite the first ten suras of the mufassal in the subh prayer, and on a journey he would recite the ummal-Qur'an and a sura in every raka

Reference

Muwatta Malik 184

In-book

Book 3, Hadith 17