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

In plain words: If a person falls sick in the first part of life, his first 24 years, he can pray to his life-breaths (Prânas), which are like the Vasus, gods who keep things alive. He asks them to stretch his life on into the middle years so he does not die young. By this prayer he gets well again.