This is another article in the chapter Probable Enormities from the classical manual on Sharia called Reliance of the Traveller. The articles are posted one by one in the order they are given in the book.
SHUNNING A MUSLIM WITHOUT RIGHT
p75.11 The Prophet (Allah bless him and give him peace) said,
“Whoever shuns his brother for a year is as though he had spilled his blood.”
(Munawi:) This means that avoiding him for a year deserves punishment in the hereafter just as spilling his blood does, and that both the person who shuns someone and he who kills someone are involved in sin, though not On the same level, for the use of a simile does not imply the parity of the simile’s subject to the thing with which it has been compared. Shafi’i holds it is unlawful to shun a Muslim for three days unless there is a valid reason such as the religious improvement of the person avoiding the other or person being avoided, or when the latter is morally corrupt or involved in reprehensible innovation (bid’a, def: w29.3) (Fayd ai-Qadir sharh al-Jami’ al-saghir (y91), 6.234).