Is it permissible for me to steal from my relative the amount of my due that he withholds, knowing that he denied me my rights after I worked for him for seven months, and I cannot sue him?

If you worked for an agreed-upon wage with a relative, and then he denied you your right, he is an oppressor and must pay you your wage, based on the Prophet's (peace and blessings be upon him) saying: "Give the laborer his wage before his sweat dries."

If he does not pay your right, and you cannot obtain it except by taking it from him without his knowledge, the majority of jurists permit this. This is the issue of "al-Zafar" (taking one's right by force or cunning), based on the Almighty's saying: "Except for those who have believed and done righteous deeds and remembered Allah much and [then] triumphed after they were wronged." They also cite the hadith of Hind bint Utbah: "Take what suffices you and your child in a reasonable manner," and the hadith of Uqbah ibn Amir regarding the right of the guest.