قَالَ لِي أَ تَدْرِي لِمَ جُعِلَ الذِّرَاعُ وَ الذِّرَاعَانِ قَالَ قُلْتُ لِمَ قَالَ لِمَكَانِ الْفَرِيضَةِ لَكَ أَنْ تَتَنَفَّلَ مِنْ زَوَالِ الشَّمْسِ إِلَى أَنْ يَبْلُغَ ذِرَاعاً فَإِذَا بَلَغَ ذِرَاعاً بَدَأْتَ بِالْفَرِيضَةِ وَ تَرَكْتَ النَّافِلَةَ[2].
“He (the Imam) (a.s.), once said to me, ‘Do you know why one and two yards are set?’ I (the narrator) said, ‘Why are they set?’ He (the Imam) said, ‘It is because of obligatory Salah (prayer). You can perform optional Salah (prayer) soon after the sun declines (to the west at noontime) until it become one yard, but if