They have spoken a lie
Al-Kāfi|Volume 8|Book 1|Chapter 517
أَبَانٌ عَنْ عُمَرَ بْنِ يَزِيدَ قَالَ قُلْتُ لِأَبِي عَبْدِ اللَّهِ (عليه السلام) إِنَّ الْمُغِيرِيَّةَ يَزْعُمُونَ أَنَّ هَذَا الْيَوْمَ لِهَذِهِ اللَّيْلَةِ الْمُسْتَقْبَلَةِ فَقَالَ كَذَبُوا هَذَا الْيَوْمُ لِلَّيْلَةِ الْمَاضِيَةِ إِنَّ أَهْلَ بَطْنِ نَخْلَةَ حَيْثُ رَأَوُا الْهِلَالَ قَالُوا قَدْ دَخَلَ الشَّهْرُ الْحَرَامُ.
517. Aban, from Umar Bin Yazeed who said: I said to Abu Abdullah عليه الصلاة والسلام that: ‘Al-Mugheira (and his people) are alleging that this day is for the night that approaches it’. So he عليه الصلاة والسلام said: ‘They lie! This day today is for the night that has passed. The people of Al-Nakhla, when they see the crescent say, ‘The Sacred Month has entered’.
- Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (16/485)
- Ṣaḥīḥ al-Kāfī, vol. 3, p. 407