The same three letters, in the same, consecutive order, can change each of the words below into new ones. Can you determine the three letters and the new words?

FAR
FEAR
WEAR
BREAD

HINT:

FA _ _ _ R

Answer:

The letters (word) THE can be inserted into each word to create a new one:

FATHER
FEATHER
WEATHER
BREATHED

Credit:  LA Times Crossword
Sylvia Bursztyn and Barry Tunick
FOUND ARTICLES DEPT.