Al-Kāfi - Volume 4 > No name
Hadith #2

2ـ إِبْرَاهِيمُ قَالَ وَكَتَبَ إِلَيْهِ عَلِيُّ بْنُ مُحَمَّدٍ الْحُصَيْنِيُّ أَنَّ ابْنَ عَمِّي أَوْصَى أَنْ يُحَجَّ عَنْهُ بِخَمْسَةَ عَشَرَ دِينَاراً فِي كُلِّ سَنَةٍ فَلَيْسَ يَكْفِي فَمَا تَأْمُرُ فِي ذَلِكَ فَكَتَبَ يَجْعَلُ حَجَّتَيْنِ فِي حَجَّةٍ إِنَّ الله عَالِمٌ بِذَلِكَ.

2. Ali ibn Ibrahim has said that Muhammad ibn al-Husayniy wrote to me saying that the son of his uncle has said in his will to perform al-Hajj for him with fifteen dinar every year; but it is not sufficient; what do you command in this matter? He (the Imam) wrote, ‘Two al-Hajj is made one al-Hajj; Allah knows it best.’”