Ibn al-Qayyim رحمه الله said:
وقال بعض الأطباء العشق امتزاج الروح بالورح لما بينهما من التناسب والتشاكل فإذا امتزج الماء بالماء امتنع تخليص بعضه من بعض ولذلك تبلغ المحبة بين الشخصين حتى يتألم أحدهما بتألم الآخر ويسقم بسقمه وهو لا يشعر
Some physicians / doctors have said that love is the merging of souls because of the harmony / compatibility and similarity between them. Just as water mixes with water, it becomes impossible to separate them from each other. Likewise, love between two people can reach such a level that one feels pain when the other is in pain, and becomes ill with their illness, even without realizing it (even though they're not connected).
كتاب روضة المحبين ونزهة المشتاقين لابن القيم
















