The ruling on giving charity and performing Hajj on behalf of a father who slaughtered for other than Allah

A message reached us from one of the listening brothers, stating: His father used to slaughter for other than Allah, according to what was told to him about it. He now wants to give charity on his behalf and perform Hajj on his behalf. He attributes the reason his father fell into that sin to the absence of scholars, guides, and advisors for him. He seeks guidance, O Shaykh?
Answer: If your father, O questioner, is known for goodness, Islam, prayer, and the like, do not believe those who say he slaughtered for other than Allah unless with certainty. You should supplicate for him, give charity on his behalf, and do the like of that, until you know with certainty that he committed shirk (associating partners with Allah). Mere hearsay without certainty is not sufficient, unless it is established for you by the testimony of two or more trustworthy people who told you that they saw and witnessed him slaughtering for other than Allah, such as those at graves, or supplicating to other than Allah. In that case, you should refrain from supplicating for him and leave his matter to Allah (Glorified and Exalted is He). This is because when the Messenger (peace and blessings be upon him) wanted to seek forgiveness for his mother, Allah did not permit him, even though she died in the pre-Islamic age of ignorance on the religion of the disbelievers. He sought permission from his Lord to seek forgiveness for her, but it was not permitted to him because she died in the outward appearance of disbelief, even if she was in ignorance. So you are the same: if it is reported to you through trustworthy people that he died in the outward appearance of shirk, such as supplicating to the dead, seeking aid from the dead, slaughtering for them, or making vows for them, then in that case, do not seek forgiveness for him and do not supplicate for him. However, do not supplicate against him and do not insult him, but refrain from him and leave his matter to Allah (Glorified and Exalted is He). If the proof was established against him, he deserved what Allah threatened those like him with. If the proof was not established against him, he will be tested on the Day of Resurrection.