479. Amīr al-mu’minīn, peace be upon him, said: The worst comrade is he for whom formality has to be observed. 
قال السيد الرضي: لاَن التكليف مستلزمٌ للمشقة، وهو شرٌ لازمٌ عن الاَخ المتَكلّفِ له، فهو شرُّ الاِخوان.
as-Sayyid ar-Raḍī says: This is because formality is inseparable from hardship and it is an eivl that is caused by a comrade for whom formality is observed. Consequently, he is the worst of all comrades.
 The friendship that is based on love and sincerity makes a man free from ceremonial formalities, but the friendship for which formalism is necessary is unstable and such a friend is not a true friend, because true friendship requires that a friend should not be a cause of trouble for the friend. If he is a cause of trouble he will prove tedious and harmful and this harmfulness is a sign of his being the worst friend.