Aishah reports that the Prophet said: "Souls are like soldiers standing in ranks: those of them with similar qualities will be friends, and those which are dissimilar in their qualities will be in conflict". [Bukhari] This hadith has several versions with different chains of transmission, all of which are authentic. This makes it highly authentic. One version which throws some light on its meaning mentions that a Makkan woman who was known to have a sense of humour and to love to play tricks travelled to Madinah where she was a guest of a woman of similar qualities. When Aishah heard of this, she said: 'My beloved husband always told the truth... [and she quoted this hadith]'. What this hadith means is that God created souls and gave them their qualities. Those of similar qualities will easily be friends when they meet in this life, while those who have different natures are likely to be in conflict. This accounts for endless cases of people getting along together when their apparent circumstances should have kept them well apart. Moreover, it tells us something about what brings good people together and what allows evil ones to flock together and even trust each other when they know that they are evil at heart. Compiled From: "Al-Adab al-Mufrad with Full Commentary: A Perfect Code of Manners and Morality" - Adil Salahi