1317 - سُئِلَ اَلصَّادِقُ عَلَيْهِ اَلسَّلاَمُ: لِمَ صَارَتِ اَلْمَغْرِبُ ثَلاَثَ رَكَعَاتٍ وَ أَرْبَعاً بَعْدَهَا لَيْسَ فِيهَا تَقْصِيرٌ فِي حَضَرٍ وَ لاَ سَفَرٍ فَقَالَ «إِنَّ اَللَّهَ تَبَارَكَ وتَعَالَى أَنْزَلَ عَلَى نَبِيِّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ كُلَّ صَلاَةٍ رَكْعَتَيْنِ فَأَضَافَ إِلَيْهَا رَسُولُ اَللَّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ لِكُلِّ صَلاَةٍ رَكْعَتَيْنِ فِي اَلْحَضَرِ وَ قَصَّرَ فِيهَا فِي اَلسَّفَرِ إِلاَّ اَلْمَغْرِبَ وَ اَلْغَدَاةَ فَلَمَّا صَلَّى صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ اَلْمَغْرِبَ بَلَغَهُ مَوْلِدُ فَاطِمَةَ عَلَيْهَا اَلسَّلاَمُ فَأَضَافَ إِلَيْهَا رَكْعَةً شُكْراً لِلَّهِ عَزَّ وَ جَلَّ فَلَمَّا أَنْ وُلِدَ اَلْحَسَنُ عَلَيْهِ اَلسَّلاَمُ أَضَافَ إِلَيْهَا رَكْعَتَيْنِ شُكْراً لِلَّهِ عَزَّ وَ جَلَّ فَلَمَّا أَنْ وُلِدَ اَلْحُسَيْنُ عَلَيْهِ اَلسَّلاَمُ أَضَافَ إِلَيْهَا رَكْعَتَيْنِ شُكْراً لِلَّهِ عَزَّ وَ جَلَّ فَقَالَ « «لِلذَّكَرِ مِثْلُ حَظِّ اَلْأُنْثَيَيْنِ» » فَتَرَكَهَا عَلَى حَالِهَا فِي اَلْحَضَرِ وَ اَلسَّفَرِ.
Hadith.1317 - Imam Jafar ibn Muhammad Al-Sadiq 
was asked:
"Why is the Maghrib prayer three rak'ahs with an additional four rak'ahs (supererogatory) afterward, and why is there no shortening of it during residence or travel?"
Imam said: "Indeed, Allah (swt), Blessed and Exalted, revealed to His Prophet ﷺ every prayer as two rak'ahs. The Messenger of Allah ﷺ added two rak'ahs to each prayer in residence and shortened them during travel, except for the Maghrib and Fajr (morning) prayers. When the Prophet ﷺ performed the Maghrib prayer, he was informed of the birth of Sayyida Fatimah Al-Zahra {S.A}, so he added a rak'ah out of gratitude to Allah (swt), Mighty and Majestic. When Hasan was born, he added two more rak'ahs out of gratitude to Allah (swt), and when Hussain was born, he added two more rak'ahs out of gratitude to Allah (swt).
He then said: 'For a male, the share is twice that of a female,' and thus he left the prayer in its current form during residence and travel."
