The Commander of the faithful narrates from the Holy Prophet,
اِنَّ المُؤمِنَ لَیسکنُ اِلَى المُؤمِنِ کما یسکنُ الظَّمانِ اِلَى الماءِ البارِدِ
A believer finds comfort in a believer in the same way that the heart of a thirsty person finds comfort in cold water.
Finding comfort and peace means to be saved from inner turmoil and fear. For example, think of a thirsty person in a desert. The thirst itself, on top of taking a physical toll on the individual’s body, affects his mind and makes him fear for his life. What will happen if he does not get any water? But then, his eyes fall upon a body of cold water. He has still not drunk from that water but already feels calm and finds comfort from within, and all that inner restlessness and fear fades away. The Prophet says that just as a thirsty person feels calmness when he gets hold of cold drinking water, a believer also feels that calmness when he is with his believing brother. This means that he feels safe with him and has nothing to fear. This is one of the signs of true faith. One may say, “Sometimes, we go meet our believing brothers and do not feel that ease and peace but rather, we feel anxious. So, what kind of criterion of faith is that?” We shouldn’t take issue with the criterion but rather with our own selves. Why are we not that source of comfort for others? Allah desires for those that believe in Him to be this way. When a believer encounters another believer and seeks to disclose his personal affairs to him, seek counsel or advice, he should not feel any worry or concern. He should not have to think twice before speaking with his brother and worry about his brother judging him or misunderstanding him. He should not have to worry about his brother thinking badly of him or revealing his secrets. He should feel secure knowing that a believer does not backbite or tell lies, he does not rejoice over his brother’s sorrows, and does not seek to benefit from his brother’s losses. A believer should be confident of these things with regards to his fellow believing brothers because a believer is supposed to be this way.