Instructions for Hasan, when returning from Siffin
Nahj al-Balāgha|Volume 1|Book 2|Chapter 31
فَإِنِّي أُوصِيكَ بِتَقْوَى اللهِ أَيْ بُنَيَّ، وَلُزُومِ أَمْرِهِ، وَعِمَارَةِ قَلْبِكَ بِذِكْرِهِ، وَالِاعْتِصَامِ بِحَبْلِهِ، وَأَيُّ سَبَبٍ أَوْثَقُ مِنْ سَبَبٍ بَيْنَكَ وَبَيْنَ اللهِ إِنْ أَنْتَ أَخَذْتَ بِهِ.
I advise you to fear Allāh, O my child, abide by His commands, fill your heart with remembrance of Him and cling to hope from Him. No connection is more reliable than the connection between you and Allāh provided you take hold of it.