Here, why does Allah U specifically say the word: ﴾بِأَيْدِيهِمْ﴿  “with their hands”, whereas writing is not done except with one’s hands?

The meaning is that the Rabbis and learned men among the Israelites wrote the Torah with their own hands and did not assign this task to anyone else, due to their strong desire to distort it. This is because, as the description: “with their hands” is from Allah U, we are sure that it is exactly as it happened.

﴾فَوَيْلٌ لَهُمْ مِمَّا كَتَبَتْ أَيْدِيهِمْ وَوَيْلٌ لَهُمْ مِمَّا يَكْسِبُونَ﴿ “Woe to them for what their hands have written and woe to them for what they earn.”

Linguistically, the word “Al-Wail” means ‘the coming of evil’. It is a word used as a curse for destruction and punishment. Thus, these people have two curses and two punishments incumbent upon them because they used to fabricate lies against Allah U and then taught them to people.