These patents commonly made provision for the acquisition of Indian slaves. That of Ponce de Leon, February 23, 1512, authorizing his voyage of discovery and colonization, provided that the Indians on the islands he might discover should be distributed among the members of the expedition, that the discoverers should be well provided for in the first allotment of slaves, and that they should “derive whatever advantage might be secured thereby.”[114] The “cédula,” issued to Lucas Vasquez de Ayllon, in 1523, authorized him to “purchase prisoners of war held as slaves by the natives, to employ them on his farms and export them as he saw fit, without the payment of any duty whatever upon them; formal apportionment of the natives was expressly forbidden.[115] In the patent to Soto, also, it was required that he should carry with him “the religious and priests, who shall be appointed by us, for the instruction of the natives of that province in our holy Catholic faith.”[116] The idea of Christianizing the natives was applied to both free and slave Indians. The taking of captives by force, and then Christianizing them was the continuation of what was known as “the exercise of a just and pious doctrine against pagans and heathens,” a doctrine common to other nations as well as to Spain. The patent of Ponce de Leon, however, made no provision for Christianizing the Indians.[117] His instructions from the crown required him to summon the natives by “requisition” to embrace the Catholic faith and yield to the king of Spain under threat of sword and slavery.[118] Consequently the Spanish explorers within the present limits of the United States continued the policy of enslaving Indians pursued by their countrymen elsewhere in the New World. A Spanish ship sailing under Esteban Gomez, a Portuguese, in 1525, coasted along the shores of North America between Nova Scotia and Florida, seeking the northwest passage, and carried a few Indians back to Spain.[119] In April, 1528, the expedition of Pánfilo de Narvaez landed near the entrance to Tampa Bay on the west coast of Florida. From this point a portion of the expedition started into the interior. The first Indians met seemed unfriendly, and five or six of them were seized.[120] On one occasion, a cacique, or chief, was held prisoner.[121] But supplies failed and discouragement followed, so the number of Indians taken was not great. In 1538, also, an expedition sent out by Hernando de Soto brought two natives from Florida to Cuba, where they were held to learn the Spanish language in order that they might act as guides and interpreters for the expedition of the following year.[122]