Numbers 12:10-11 And the cloud departed from off the tabernacle; and, behold, Miriam became leprous, white as snow: and Aaron looked upon Miriam, and, behold, she became leprous. And Aaron said unto Moses, Alas, my lord, I beseech thee, lay not the sin upon us, wherein we have acted foolishly, and wherein we have sinned.
The response of Aaron to the cloud departing and Miriam becoming leprous was to admit sinning and acting foolishly, to repent, to beg forgiveness, and to ask not to lay the sin upon them. He was enabled to clearly see the effects of sin in the cloud and the leprosy. Seeing the consequences of sin and making the connection drove him to repent and ask forgiveness.
We don’t always make the connection between our own sin and guilt and the consequences of it. We need the Word of Law to connect the dots, to convict of sin, and to feel the guilt. The Law shows us our Sin and the Gospel shows us our Savior. We see; then we admit the sin and ask forgiveness. The Holy Spirit moves us to repent and believe and God grants life.
Aaron saw that he acted foolishly after he saw the effect. At the time it didn’t seem foolish, but reasonable. He might not have acted so foolishly at the time if he could have seen the sin for what it is. And so it is for us: we are deceived, and we can come up with many excuses and supposed reasons for our behavior, until God reveals the sin, its cause and effect. Then we admit guilt. It goes better for us when we are often in the Word, repent instantly, and believe unceasingly. Foolishness and leprosy may be avoided by early and often repentance.