The first American-born pope said he planned to gradually resume his regular activities with God's help and the continued prayers of the faithful.

During his Angelus address, Leo reflected on one of Jesus' best-known teachings, "Give therefore to the emperor the things that are the emperor's, and to God the things that are God's," urging Christians to live with integrity and resist hypocrisy.

His return came sooner than expected after doctors initially anticipated a hospital stay of approximately one week following Tuesday's surgery.

As he departed the hospital on Saturday, the pope told a reporter in English that he was doing "much better."

Claire Holland, visiting from Jacksonville, Fla., told The Associated Press she felt "very blessed" to witness the pope's return.

"I think there have been millions and millions of prayers. And he is a strong determined man, and I am so happy that he is feeling well enough to do this," Holland said.

The surgery marked the first major health crisis of Leo's 17-month pontificate. Doctors confirmed that the tumor was adenocarcinoma, the most common form of lung cancer.

Doctors are conducting further testing on the tumor and surrounding lymph nodes to determine the extent of the disease and whether additional treatment, including chemotherapy, immunotherapy or targeted therapy, may be necessary.

The pope is scheduled to visit Uruguay, Argentina and Peru from Nov. 6 through Nov. 17, a demanding itinerary that includes a dozen flights and two helicopter rides to high-altitude destinations.

His surgeon, Dr. Stefano Margaritora, told Vatican News on Saturday that the pope appears well enough to go on the trip.

"The Holy Father has put his heart and soul into his recovery," Margaritora said, adding that he expected Leo to recover fully from the surgery "in another 10 days or so."

"As for a long trip involving air travel in about three weeks, I would say there are no clinical reasons why it should not take place," Margaritora said.

Fox News’ Courtney Walsh and The Associated Press contributed to this report.