Hadithcore
Mishkat al-Masabih, 849, 850

Jabir b. Samura said that the Prophet (ﷺ) used to recite in the sunset prayer on Thursday evening, “Say, O unbelievers,”1 and “Say, He is God one God.”2 1. Al-Qur’an; 109 2. Al-Qur’an; 112 [Baghawi] transmitted it in <i>Sharh as-sunna</i>; and Ibn Majah transmitted it from Ibn ‘Umar, but did not mention Thursday evening.

وَعَنْ جَابِرِ بْنِ سَمُرَةَ قَالَ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقْرَأُ فِي صَلَاةِ الْمَغْرِبِ لَيْلَةَ الْجُمُعَةِ: (قُلْ يَا أَيُّهَا الْكَافِرُونَ) و (قل هُوَ الله أحد) رَوَاهُ فِي شرح السّنة وَرَوَاهُ ابْنُ مَاجَهْ عَنِ ابْنِ عُمَرَ إِلَّا أَنه لم يذكر «لَيْلَة الْجُمُعَة»

References1 variant
In-Book Reference
Book 4, Hadith 275