Sulaiman b. 'Abd al-Rahman al-Dimashqi said about this tradition that al-Walid said:I heard Abu 'Amr al-Auza'i say: The word sirrahu means beginning of the month.
حَدَّثَنَا سُلَيْمَانُ بْنُ عَبْدِ الرَّحْمَنِ الدِّمَشْقِيُّ، - فِي هَذَا الْحَدِيثِ - قَالَ قَالَ الْوَلِيدُ سَمِعْتُ أَبَا عَمْرٍو - يَعْنِي الأَوْزَاعِيَّ - يَقُولُ سِرُّهُ أَوَّلُهُ .
AbuDaud
Fasting (Kitab Al-Siyam) • Hadith 2330