圣经里有许多处很明显的说到光。在马太六章，主耶稣说到心里的光的问题，主说，“眼睛就是身上的灯。” 注意，主在这里不是说眼睛就是身上的光，乃是说眼睛就是身上的灯。光是神的，灯是我们的。光在神的话里，灯在我们身上。灯乃是我们得着光的地方。换句话说，灯是神摆光的地方，灯是我们接受光的地方，灯也是我们释放光的地方。要神的话在我们身上光照，那就必须在我们身上有灯。这个灯是我们的眼睛。“你的眼睛若纯一（‘膫亮’照原文可译作‘纯一’），全身就光明。你的眼睛若恶（‘昏花’照原文可译作‘恶’或‘坏’），全身就黑暗。”（22～23。）如果我们要全身都亮，都充满光，主告诉我们有一个条件，就是我们的眼睛必须纯一。
甚么叫作眼睛的纯一呢？我们的眼睛虽然有两个，但是焦点只有一个，两个眼睛同时只看一件东西。假使人的眼睛有病，不纯一，两个眼睛就有两个焦点，同时看见了两件东西，看得都不清楚。眼睛要看得准，就只可有一个焦点，不可有两个焦点。我们要得着光，有没有光是一个问题，眼睛看得见看不见也是一个问题。我们如果没有蒙恩典，没有蒙怜悯，光就不在我们身上；我们已经蒙了恩典，已经蒙了怜悯，光就已经在我们身上。所以我们现在的难处不是光上，乃是在眼睛上。眼睛不纯一，光就不能彰显。许多人眼睛不纯一，不是只看一件东西，而是同时看两件东西，或者把一件东西看成两件东西，所以光在他们身上是不清楚的，甚至是完全黑暗的。
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The Eyes Must Be Single (1) — Matt. 6:21
The Bible speaks clearly of light in many places. In Matthew chapter six, the Lord Jesus speaks about the light within our heart. The Lord says, “The eye is the lamp of the body.” Note that the Lord does not say that the eye is the light of the body, but that the eye is the lamp of the body. Light belongs to God; the lamp belongs to us. Light is in God’s Word; the lamp is within us. The lamp is the place where we receive the light. In other words, the lamp is where God places His light, the place where we receive the light, and the place where we release the light. For God’s Word to shine upon us, there must be a lamp within us. This lamp is our eye. “If your eye is single (it can be translated as pure according to the original text), your whole body will be full of light. If you eye is bad (may also be translated as evil according to the original text), your whole body will be full of darkness.” (Matt. 6:22–23) If we want our whole body to be bright and filled with light, the Lord tells us that there is one condition — our eyes must be single.
What does it mean for the eye to be single? Although we have two eyes, we only have one focus, and both eyes can see one thing at a time. If a person’s eyes are diseased or impure, they will have two focuses, and they will see two things at the same time, but neither will be clear. To see clearly, the eyes must have only one focus, not two. To receive light, two issues must be addressed — whether there is light, and whether the eyes can see it. If we have not received grace and mercy, the light is not upon us; but if we have received grace and mercy, the light is already upon us. Therefore, our problem today is not with the light — it is with our eyes. When the eyes are not single, the light cannot be manifested. Many people’s eyes are not single — they do not look at one thing, but at two things at the same time, or they see one thing as two. Thus, the light is not clear on them, or even completely dark.