Srimad Bhagavatam Canto 10, Chapter 20, Text 21

 SB 10.20.21

pitvapah padapah padbhir
 asan nanatma-murtayah
prak ksamas tapasa sranta
 yatha kamanusevaya
The trees had grown thin and dry, but after they drank the newly fallen rainwater through their feet, their various bodily features blossomed. Similarly, one whose body has grown thin and weak from austerity again exhibits his healthy bodily features upon enjoying the material objects gained through that austerity.
The word pada means foot, and pa means drinking. Trees are called padapa because they drink through their roots, which are likened to feet. Upon drinking the newly fallen rainwater, the trees in Vrndavana began to manifest new leaves, sprouts and blossoms, and they thus enjoyed new growth. Similarly, materialistic persons often perform severe austerities to acquire the object of their desire. For example, politicians in America undergo grueling austerities while traveling about the countryside campaigning for election. Businessmen also will often deny personal comfort to make their business successful. Such austere persons, upon acquiring the fruits of their austerity, again become healthy and satisfied, like trees eagerly drinking rainwater after enduring the austerity of a dry, hot summer.
Srimad Bhagavatam Canto 10, Chapter 20, Text 20
Srimad Bhagavatam Canto 10, Chapter 20, Text 22