Last will for Hasan and Husayn
Nahj al-Balāgha|Volume 1|Book 2|Chapter 47
وَعَلَيْكُمْ بِالتَّوَاصُلِ وَالتَّبَاذُلِ، وَإِيَّاكُمْ وَالتَّدَابُرَ وَالتَّقَاطُعَ. لَا تَتْرُكُوا الْأَمْرَ بِالْمَعْرُوفِ وَالنَّهْيَ عَنِ الْمُنْكَرِ فَيُوَلَّى عَلَيْكُمْ أَشْرَارُكُمْ، ثُمَّ تَدْعُونَ فَلَا يُسْتَجَابُ لَكُمْ.
You should keep to a respect for kinship and spending for others. Avoid turning away from one another and severing mutual relations. Do not give up bidding for good and forbidding from evil lest the mischievous gain positions over you, and then if you will pray, the prayers will not be granted.