Earlier in John 9:4, Jesus had told His disciples, “As long as it is day, we must do the work of Him who sent Me.” In this verse, and for the first time, Jesus wasn’t just speaking about Himself & His mission here on earth but now included His disciples as partners in His Gospel work. You must work in the light for, “God is light; and in Him there is no darkness at all.” (I John 1:5) Which here in this verse emphasizes God’s attributes of moral purity & omniscience. Thus, even though you’re in the world, you will not stumble because the truth of God’s light will illuminate & clear your path of confusion & deception. But if you walk in the darkness of self-reliance & independence from God… you will stumble. That’s because all your beliefs, ethics, and attitudes are the opposite of God’s.