Some of the letters in the New Testament start off by exclaiming a joy because the authors had found out fellow believers were being faithful to God. For example 3 John 3-4 says,
"It gave me great joy to have some brothers come and tell me about your faithfulness to the truth and how you continue to walk in the truth. I have no greater joy than to hear that my children are walking in the truth."
John exclaims that he has NO greater joy than that of fellow believers walking in the truth. With this kind of joy, it seems as though he would draw encouragement as well. Although the Bible does not directly say that, seeing others he has mentored continue to grow and continue in what he has taught them, would very possibly have that outcome. If this is the case, we ought to strive to continue to be faithful as well. Not only do we receive a better relationship with God, but also we could possibly be an encouragement to someone else. At the very least, we could bring someone joy. On the other end of the spectrum, your
faithlessness could have the opposite effect on a person; you could be the one to bring them sadness or discouragement. You never know when your level of faith could have a very impacting impression on someone.