What letters are used to answer an oath?

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An oath can be answered using four letters: two for negation (*nafy*), which are *Ma* (ما) and *La* (لا), and two for affirmation (*ithbāt*), which are *Inna* (إن) and the open *Laam* (ل). The diacritically marked *Inna* (إن) can substitute for the negating *Ma*, as seen in Quran 9:107. When someone says, *Wallahi af'alu* (By Allah, I do [it]) without an intervening letter, the implied particle is *La* (لا), meaning the oath is meant in the sense of negation, consistent with its usage in Quran 12:85 ("La tafta'u" - You do not cease) and poetic usage.