Is it permissible to give charity on behalf of the deceased after their death, and what is the relation of this to the hadith: "The deeds of the son of Adam cease except for three..."?

The correct view is that charity given on behalf of the deceased reaches them and its reward benefits them. This is based on the hadith of the man who asked the Prophet, peace and blessings be upon him, about giving charity on behalf of his deceased mother, and the Prophet answered him with "Yes." This does not contradict the hadith, "When a person dies, his deeds are cut off except for three..." because the reaching of the reward of charity and supplication to the deceased is from the actions of others on their behalf, whereas the hadith about deeds being cut off means that the deceased's own actions for themselves are cut off, except for what they were a cause of before their death. So, a righteous child is considered part of one's own earning, and the knowledge one leaves behind, and ongoing charity (waqf) are all matters for which the deceased was a cause.