The writer speaks of the actions and lifestyles of righteous people and wicked people as if they were a "path" or "way" upon which they walk. AT: "the lifestyle of righteous people ... The lifestyle of the wicked" (See: [[rc://en/ta/man/translate/figs-metaphor]])
# the path of righteous people is like the first light that grows brighter
The writer compares the path of righteous people to the sunrise, meaning that they are safe because they have light to see where they are walking. AT: "righteous people walk along their path safely because the morning sun shines on it and grows brighter" (See: [[rc://en/ta/man/translate/figs-simile]])
# the first light
This refers to the dawn or sunrise.
# until the fullness of the day comes
This refers to the time of day at which the sun shines the brightest. AT: "until the sun shines most brightly" or "until full daylight" (See: [[rc://en/ta/man/translate/figs-idiom]])