Tearing for an Adopted Son on His Adoptive Father's Passing

An adopted son, whose adoptive father has passed away, is he obligated to tear his clothes, or is it prohibited as bal tashchit?

He should tear his clothes, and certainly there is no prohibition of bal tashchit. Since he is greatly distressed by this news, he recites the blessing 'Baruch Dayan HaEmet' with Shem and Malchut.

It is written in the responsa Shaar Ephraim (grandfather of the Chacham Tzvi) in Siman 91 regarding a man who converted a slave and a maidservant and raised them in Torah, and he died. He wrote that the converts should mourn and tear their clothes for the one who raised them in Torah, and he proved this from the statement: the loss of a father and the loss of a teacher, the loss of a teacher takes precedence, as the teacher brings him to life in the World to Come. Therefore, the one who converted them is greater than their father, and they should tear their clothes as for a teacher. Some have written to infer from this that an adopted son should tear his clothes for his adoptive father who passed away, since he certainly raised him in Torah and brought him to life in the World to Come. However, it can be countered that from the Gemara in Bava Metzia it is proven that a father is considered to bring him to life in this world (when he is not his teacher), and even if he raised him according to law and justice, why should it be said that he is obligated to tear for an adoptive father as for a teacher. However, even if we say that it is not a strict obligation, nevertheless, it is certainly not less than for a righteous person who is mourned, and according to the basic law, one should tear, and although it is customary to be lenient in this, as the Rema wrote in Siman 340, paragraph 6, nevertheless here, where he has great sorrow over his death, the poskim wrote that it is proper to tear. And since according to the basic law one tears for a righteous person, there is no prohibition of bal tashchit.