IHSARU ‘L-HAJJ احصارالحج
The hindering of the Pilgrimage. For example: If a pilgrim be stopped on his way by any unforseen circumstance, such as sickness or accident, he is required to send an animal to be sacrificed in the Sacred City. (Hidayah, Arabic ed. vol. i. p. 184.) This injunction is founded upon the teaching of the Qur’an, Surah ii. 193. “And if he be prevented; then send whatever offering shall be easiest: and shave not your heads until the offering reach the place of sacrifice. But whoever among you is sick, or hath an ailment of the head, must expiate by fasting, or alms, or a victim for sacrifice. And when ye are secure (from hindrances) then he who delights in the visitation (‘Umrah) of the holy place until the Pilgrimage, shall bring whatever offering shall be the easiest. But he who that nothing to offer shall fast three days in the Pilgrimage and seven days when ye return; they shall be ten days in all.”

Based on Hughes, Dictionary of Islam