If anything ails him in that (third) age, let him say: 'Ye Prânas, ye Âdityas, extend this my third libation unto the full age, that I, the sacrificer, may not perish in the midst of the Prânas or Âdityas.' Thus he recovers from his illness, and becomes whole.

In plain words: If a person falls sick in old age, he can ask his life-breaths, like the Âdityas, to carry his life on to its full length. By this prayer he gets well again.