What is the ruling on praying at a grave out of necessity?

Praying at a grave, by making it a qibla (definition) (direction of prayer), prostrating on it, or performing salah (definition) near it, is impermissible. This is due to the prohibition by the Prophet, peace and blessings be upon him, as mentioned in the hadiths of Abu Sa'id al-Khudri and Ali ibn Abi Talib. Anas ibn Malik, may Allah be pleased with him, was once praying towards a grave when Umar ibn al-Khattab called out to him, "The grave! The grave!" whereupon Anas moved away from it. Many scholars consider prayer at a grave to be invalid, while others deem it valid but reprehensible, and do not require its repetition. This is the view of Malik, Shafi'i, and Ahmad in one narration.