Sahih Muslim , Book 20, Hadith 4583 (USC-MSA) ⓘ
It has been narrated (through a different chain of transmitters) on the authority of Salim b. al-Ja'd who said: I asked Jabir: How many were you on the Day of Hudaibiya? He said: One thousand and four hundred.
وَحَدَّثَنَا عُثْمَانُ بْنُ أَبِي شَيْبَةَ، وَإِسْحَاقُ بْنُ إِبْرَاهِيمَ، قَالَ إِسْحَاقُ أَخْبَرَنَا وَقَالَ، عُثْمَانُ حَدَّثَنَا جَرِيرٌ، عَنِ الأَعْمَشِ، حَدَّثَنِي سَالِمُ بْنُ أَبِي الْجَعْدِ، قَالَ قُلْتُ لِجَابِرٍ كَمْ كُنْتُمْ يَوْمَئِذٍ قَالَ أَلْفًا وَأَرْبَعَمِائَةٍ .
also referenced under: Book 33, Hadith 111 (In-Book) & Hadith 1856 (Reference)