Does the Writings say that reincarnation is not true, nor possible?
The Writings of the Bab speak of “return”, that the souls of the Prophets, the Saints, and “certain Chosen Ones” will RETURN in every Dispensation. In other words, the soul of Muhammad returned as Mulla Husayn, the first believer in The Bab. The Bab was the “return” of Imam Mahdi, a young boy who died falling into a well 1000 lunar years before The Bab declared He was the Mahdi !
Baha’u’llah wrote that he was the return of “Jesus, the spirit of God”. ‘Abdu’l-Baha said that “human souls” do not return to THIS planet. The Sufis taught that when a man became a WALI (“Saint”) he no longer had a human soul, but an angel soul or a divine soul. This occurred when the Seeker extinguished his “ego” (human soul), and his nafs (self) is fana’ (“blown out like a candle”). Other incarnations on other planets are not ruled out, and seem to be at least hinted at in some Writings and pilgrim notes. The souls of Prophets are pre-existent, and thus not human souls. The souls of the Saints are not “human souls” because they have extinguished their human souls and the only eternal thing that remains in them is the Divine, or Angelic, Soul.