The Sufficient (Vol 1) · Hadith 1253 (#Ḥadīth #2)
Chapter 116 | The Birth of al-Husayn ibn Ali
2ـ عِدَّةٌ مِنْ أَصْحَابِنَا عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنْ عَلِيِّ بْنِ الْحَكَمِ عَنْ عَبْدِ الرَّحْمَنِ الْعَرْزَمِيِّ عَنْ أَبِي عَبْدِ الله قَالَ كَانَ بَيْنَ الْحَسَنِ وَالْحُسَيْنِ طُهْرٌ وَكَانَ بَيْنَهُمَا فِي الْمِيلادِ سِتَّةُ أَشْهُرٍ وَعَشْراً.
2. A number of our people has narrated from Ahmad ibn Muhammad from Ali ibn al-Hakam from ‘Abd al-Rahman al-‘Arzami from Abu ‘Abdallah who has said the following. “The time between the birth of al-Hasan and the conception for al-Husayn was like one menstuaral cycle and the time between the birth of the two was six months and ten days.”
Gradings are classical jarḥ-wa-taʿdīl, name-matched to a rijāl index (not individually re-verified).