How can one reconcile the Hadith "Seeking knowledge is an obligation upon every Muslim" with considering knowledge—such as medicine and other fields essential for the well-being of worldly affairs—a communal obligation (fard kifaya)?

Knowledge is of two types: an individual obligation (fard al-ayn) and a collective obligation (fard al-kifaya).

Individual obligation (fard al-ayn) is that which an accountable person cannot afford to be ignorant of, such as the rulings concerning beliefs (aqidah), purification (tahara), and prayer (salat). This is what is incumbent upon a man for himself, as it is narrated that the Prophet (peace be upon him) said: "Seeking knowledge is an obligation upon every Muslim."

Collective obligation (fard al-kifaya) is acquiring what people cannot do without for the establishment of their religion from the Islamic sciences, such as the Quran, Hadith and their related sciences, usul (principles of Islamic jurisprudence), fiqh (Islamic jurisprudence), grammar (nahw), and language.