Proverbs 4:18 says, "But the path of the righteous....grows brighter and brighter until full daylight."
The Bible "light" doesn't get brighter - it never changes - it's a person's direction & course of life which gets brighter.
w11 9/15 p. 14 par. 15 - "When spiritual light on some matter gets brighter, do you try to understand the underlying Scriptural reasons for the adjustment? (Prov. 4:18)"
w07
6/1 pp. 22-23 par. 9 - "...a
Christian elder in his 80’s,...says, “I’m just absolutely in
love with the truth, and I’m thrilled to see how the light of
truth gets brighter and brighter.”
w87 5/15 p. 28 - "Similarly, spiritual light gets brighter for Jehovah’s people as time goes on."
w81 12/1 p. 17 par. 3 - "But as the light gets brighter..."
w61 2/1 p. 80 par. 13 - "...we will study the Scriptures and keep up with the advancing understanding of the truth as its light gets brighter and brighter."