What is the ruling on praying on the last Wednesday of Safar to repel بلاء (affliction), and what is its validity and evidence?

The prayer mentioned is an innovation, having no basis or evidence. Rather, it is fabricated and denounced. It has been authentically reported from the Messenger of Allah, peace and blessings be upon him, that he said: "Whoever performs a deed that is not in accordance with our command will have it rejected," and he said: "Whoever introduces into this matter of ours that which does not belong to it will have it rejected." And whoever attributes it to the Prophet, peace and blessings be upon him, or to the Companions, has committed a grave fabrication.