Bukhari

And if he swore an oath out of fear that if he did not swear, some oppressor would kill him or inflict some other punishment upon him, then likewise, anyone who is forced and is afraid, it is obligatory upon every Muslim to help him, to repel the oppressor’s oppression from him, to fight for his rescue, and not to leave him in the hands of the enemy. Then, if he fought in support of the oppressed and, with the intention of rescuing him, killed the oppressor, then retaliation (qisas) will not be obligatory upon him (nor will blood money be obligatory). And if someone is told: “Drink wine, or eat carrion, or sell your slave, or admit to such-and-such a debt (or write its document), or give such-and-such a thing as a gift, or annul a contract, otherwise we will kill your religious father or brother,” then it is permissible for him to do these things, because the Prophet (peace and blessings be upon him) said: “A Muslim is the brother of another Muslim.” And some people say: If he is told: “Drink wine, or eat carrion, otherwise we will kill your son or father or a close relative—brother, uncle, maternal uncle, etc.—then it is not permissible for him to do these things, nor will he be considered compelled (mudtar). Then, some of these people contradicted themselves in another issue. They say: If someone is told: “We will kill your father or son unless you sell this slave of yours, or admit to such-and-such a debt, or give such-and-such a thing as a gift,” then by analogy, all these transactions are valid and effective. But in this issue, we act upon benevolence (ihsan) and say that in such a situation, the sale, gift, and every contract, admission, etc., will be invalid. Some of these people have also differentiated between blood relatives and non-blood relatives, for which there is no evidence from the Qur’an or Hadith. And the Prophet (peace and blessings be upon him) said that Ibrahim (peace be upon him) said to his wife Sarah: “She is my sister in the way of Allah, in terms of religion.” And Ibrahim al-Nakha’i said: If the one demanding the oath is an oppressor, then the intention of the one swearing is considered; and if the one demanding the oath is oppressed, then his intention is considered.

Narrated `Abdullah bin `Umar: Allah's Apostle said, "A Muslim is a brother of another Muslim. So he should neither oppress him nor hand him over to an oppressor. And whoever fulfilled the needs of his brother, Allah will fulfill his needs."