What is the meaning of al-istinjāʾ, al-barājim, and al-sibṭ? And how many rakʿahs are there in the Salat al-Tahajjud?

The meanings of "Istinja" (washing after defecation/urination), "washing the knuckles," and the number of Rak'ahs for Tahajjud prayer have been reviewed in previous fatwas.

As for the word "Sabt": If it is pronounced with a shaddah on the "Sīn" and sukoon on the "Bā'" (السِّبْط), it means a grandchild (child of a child). If it is pronounced with a shaddah on the "Sīn" and a kasra or fatḥa on the "Bā'" (السَّبِط or السَّبَط), it describes straight, uncurly hair, and also refers to a man of good stature and well-proportioned. "Al-Asbāt" (الأسباط) refers to grandchildren, and is also used to denote the tribes of the Children of Israel.