 His last work was a Spanish paraphrase of the Psalms, which was printed with the text, under the title "Las Alabanças de Santitad" (Amsterdam, 1671), and, as is stated in the introduction, was written in seven months.The work was dedicated to Isaac Senior Teixéyra, financial agent, in Hamburg, of Queen Christina of Sweden, and was praised by many ḥakamim, scholars, and poets in Hebrew, Latin, and Spanish verses.Jacob wrote also a dialogue ("Colloquium Middelburgense") between a rabbi and a Christian scholar on the value of the Christian dogmas; and he left in manuscript "Disputaciones con Diferentes Theologos de la Cristiandad".