Who has precedence in custody when separated parents have a young or insane child?

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When a couple separates and they have an infant or insane child, the mother has the greatest right to their custody, provided she meets all the necessary conditions, regardless of whether she is male or female. This is the consensus view held by Yahya al-Ansari, Az-Zuhri, Ath-Thawri, Malik, Ash-Shafi'i, Abu Thawr, Ishaq, and the People of Opinion, with no known dissenters. The basis for this is the narration from 'Abdullah ibn 'Amr ibn al-'As where a woman stated her closeness to the child (womb, breast, lap) and the father's intent to take him, to which the Prophet (peace be upon him) replied, 'You are more entitled to him unless you marry.' Furthermore, Abu Bakr As-Siddiq ruled in favor of 'Asim's mother over 'Umar ibn Al-Khattab, stating that her scent, feel, and gentleness are better for him. The mother is closer and more compassionate than anyone except the father, and the father cannot personally undertake custody but must delegate it to his wife, and the mother has precedence over the father's wife.