The ruling regarding custody when parents separate their domicile under safe conditions.
Chapter on Who is More Entitled to Child Custody
Al-Mughni
Book of Maintenance (Nafaqāt)
Primary text
When the parents separate their domicile under safe conditions for both the journey and the destination, the father is more entitled to custody. This view is held by Shurayh, Malik, and Al-Shafi'i. The rationale is that the divergence of domicile gives precedence to the father, as he typically undertakes the upbringing, instruction, and securing of the child's lineage; his absence from his own location compromises these duties.
Supporting text
The Hanafis hold that if the father moves, the mother retains custody. If the mother moves to the place where the marriage originated, she retains custody; if she moves elsewhere, the father has the greater right. Abu Hanifa is narrated to have differentiated: if the mother moves from a city (balad) to a village (qaryah), the father has priority; if she moves to another city, she has priority, based on the belief that instruction and development are better facilitated in a city. This reasoning is refuted because the father's role in the child's discipline and lineage preservation is paramount, and loss of lineage occurs if he is absent from his location, similar to a village scenario.