Ali ibn Ibrahim, from his father, from Ibn Abi Umayr, from Hafs ibn al-Bakhtari, from Abu Abdullah عليه السلام, who said:
Imam عليه السلام said: "The shroud is torn (opened) when the deceased is placed in his grave, from the side of his head."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 1, p. 486