Narrated by Muhammad ibn Ya’qub from Muhammad ibn Yahya from Ahmad ibn Muhammad from Hammad from Hariz from Zurarah, who said:
Abu Ja’far عليه السلام said: "Estimation (taharri) is always sufficient when the direction of the qiblah is not known."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 2, p. 49