Al-Kāfi - Volume 3 > Optional Salah (Prayer) On Friday
Hadith #3

3ـ جَمَاعَةٌ عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنِ الْحُسَيْنِ بْنِ سَعِيدٍ عَنْ فَضَالَةَ أَوْ عَنْ مُحَمَّدِ بْنِ سِنَانٍ عَنِ ابْنِ مُسْكَانَ عَنْ عَبْدِ الله بْنِ عَجْلاَنَ قَالَ قَالَ أَبُو جَعْفَرٍ (عَلَيْهِ الْسَّلام) إِذَا كُنْتَ شَاكّاً فِي الزَّوَالِ فَصَلِّ رَكْعَتَيْنِ فَإِذَا اسْتَيْقَنْتَ فَابْدَأْ بِالْفَرِيضَةِ.

3. A group has narrated from Ahmad ibn Muhammad from al-Husayn ibn Sa‘id from Fadalah or Muhammad ibn Sinan from ibn Muskan from ‘Abd Allah ibn ‘Ajalan who has said the following: “Abu Ja’far, ‘Alayhi al-Salam, has said, ‘If you have doubts about Zawal (declining of the sun toward the west at noontime), perform two Rak‘at. When you become certain of Zawal, then begin performing obligatory Salah (prayer).”’