عَلِيُّ بْنُ مُحَمَّدِ بْنِ بُنْدَارَ عَنْ أَبِيهِ عَنْ مُحَمَّدِ بْنِ عَلِيٍّ الْهَمَذَانِيِّ أَنَّ رَجُلًا كَانَ عِنْدَ الرِّضَا ( عليه السلام ) بِخُرَاسَانَ فَقُدِّمَتْ إِلَيْهِ مَائِدَةٌ عَلَيْهَا خَلٌّ وَ مِلْحٌ فَافْتَتَحَ ( عليه السلام ) بِالْخَلِّ فَقَالَ الرَّجُلُ جُعِلْتُ فِدَاكَ أَمَرْتَنَا أَنْ نَفْتَتِحَ بِالْمِلْحِ فَقَالَ هَذَا مِثْلُ هَذَا يَعْنِي الْخَلَّ وَ إِنَّ الْخَلَّ يَشُدُّ الذِّهْنَ وَ يَزِيدُ فِي الْعَقْلِ .
4. Ali ibn Muhammad ibn Bandar has narrated from his father from Muhammad ibn Ali al-Hamadaniy who has said the following: “A man in Khurasan once was with al-Rida’ , and the table-spread with food inside, vinegar and salt, was brought to him. He (the Imam) began with vinegar and the man said, ‘I pray to Allah to keep my soul in service for your cause, have you commanded us to begin with salt?’ He (the Imam) said, ‘This is like that’, meaning vinegar, ‘and that vinegar strengthens the mind and increases the ability to understand.’” 