Question: Is it wrong to say salām to Imam Hussein (as) during the qunūt of prayer? What is the ruling if a person has done so in the previous prayers?

Answer: In general, addressing other than God in prayer invalidates the prayer. However, the previous prayers - which he did not know the ruling nor thought that it may be wrong - are correct, but according to the obligatory caution, he must perform sijdah of inadvertence.