The Bible says that sin not only has an affect upon us, it also affects our relationship with other people. The Bible is explicit in the way sin effects believers.

Lack of Compassion

The sincere concern believers have for unbeliever's is affected by sin in our life. When we are in sin, thoughts of unbelievers and their needs do not arise. Those who are trapped in sin are indifferent to the plight of the lost. Contrast this to the attitude of the Lord Jesus.

But when He saw the multitudes, He was moved with compassion for them because they were weary and scattered, like sheep having no shepherd (Mat 9:36)

Wrong Interests

We tend to be interested in everything except that which is of utmost importance. Consequently opportunities to testify to our faith in Christ are bypassed.

We do not leave the proper impact on those whom we meet:

For if I make you sorrowful, then who is he who makes me glad but the one who is made sorrowful by me (2Cr 2:2).

We fail to see that those whom God brings us into contact are people who need to know Christ. Our zeal to testify to Christ has been lost.

Summary

Sin can cause us to lose compassion for the lost as well as lose interest in testifying to our faith.