The pronoun "he" refers to Jesus. Here "a third time" means "time number 3." Alternate translation: "Jesus said to him a third time" (See: [[rc://en/ta/man/translate/translate-ordinal]])
Here "sheep" is a metaphor that represents those who belong to Jesus and follow him. Alternate translation: "Care for the people I care for" (See: [[rc://en/ta/man/translate/figs-metaphor]])