▁thus ▁the ▁father ' s ▁first born ▁son ▁was ▁not ▁that ▁of ▁the ▁mother ). ▁And ▁thus ▁where ▁a ▁b ach elor ▁married ▁a ▁vir gin ▁( so ▁that ▁the ▁first born ▁son ▁of ▁the ▁father ▁would ▁also ▁be ▁the ▁first born ▁son ▁of ▁the ▁mother ) ▁might ▁the ▁first born ▁son ▁also ▁take ▁a ▁double ▁portion ▁in ▁his ▁mother ' s ▁estate ? ▁Rav ▁N ah man ▁bar ▁Isaac ▁replied ▁that ▁ ▁says , ▁" for ▁he ▁[ the ▁first born ▁son ] ▁is ▁the ▁first - f ruits ▁of ▁his ▁[ the ▁father ’ s ] ▁strength ," ▁from ▁which ▁we ▁can ▁infer ▁that ▁the ▁law ▁applies ▁to ▁the ▁first ▁f ruits ▁of ▁the ▁father ' s ▁strength ▁and ▁not ▁the ▁first - f ruits ▁of ▁the ▁mother ' s ▁strength . ▁The ▁Gem ara ▁replied ▁that ▁ ▁teach es ▁that ▁though ▁a ▁son ▁was ▁born ▁after ▁a ▁mis car riage ▁( and ▁thus ▁did ▁not ▁" open ▁the ▁w omb " ▁and ▁is ▁not ▁regarded ▁as ▁a ▁first born ▁son ▁for ▁purposes ▁of ▁" san ct ification ▁to ▁the ▁Lord " ▁and ▁" re dem ption ▁from ▁the ▁priest " ▁in ▁) ▁he ▁is ▁non eth eless ▁regarded ▁as ▁the ▁first born ▁son ▁for ▁purposes ▁of ▁inheritance . ▁ ▁thus ▁implies ▁that ▁only ▁the ▁son ▁for ▁whom ▁the ▁father ' s ▁heart ▁gr ieves ▁is ▁included ▁in ▁the ▁law , ▁but ▁a ▁mis car riage , ▁for ▁which ▁the ▁father ' s ▁heart ▁does ▁not ▁gr ieve , ▁is ▁ex