But when the Holy Spirit controls our lives he will produce this kind of fruit in us: love, joy, peace, patience, kindness, goodness, faithfulness.
– Galatians 5:22

In our text we see that faithfulness is a fruit of the spirit but in order for us to have a better understanding, we must first be clear on what the fruit is.
To do this we must look at the context of the passage and see what the fruit if the spirit is.
First we must note that the fruit is in contrast with the fruits or deeds of the flesh seen in verse 19. The deeds of the flesh are natural products if the flesh and is the identity of people ruled by the flesh. On the other hand the fruit of the Spirit is singular with numerous manifestation, and they all are a unit. It is evident in a life that is lived and led by the spirit. It is also the character of the Spirit being incorporated in us by the Holy spirit after we have been regenerated. It is also the very character of God which He graciously shares with us His children through His Spirit.”But you are to be perfect, even as your Father in heaven is perfect.” [Matthew 5:48] everything the Lord does is to make us to conform totally to His image, and this He does in us through the Holy Spirit.
Secondly, we must know that as mentioned in verse 19 an unbeliever might not exhibit or posses all deeds of the flesh but will posses more than two. The Believer possesses and manifests all the fruit. Although they might not all manifest at a time and may take time to be evident in a believers life but he does posses all fruit.
No man can produce any of the manifestation of the fruit of the Spirit by his own effort except it is done by God through His spirit.

O Ephraim! Stay away from idols! I am living and strong! I look after you and care for you. I am like an evergreen tree, yielding my fruit to you throughout the year. My mercies never fail.

– Hosea 14:8

all good fruits comes from God and He gives us this fruits, although people might be able to imitate or produce what seem like this fruits but it cannot last and lacks substance. For the believer they are all an integral part of them and becomes the very essence of their life
Having given an overview of what the fruit is, what then is the fruit of the Spirit?
* It is an outward indicator of salvation. Although we are saved by faith, it is an indicator to people and a testament of the transformation that has happened in us and further strengthen our faith.
* A believer’s sonship in God and citizenship is manifested by the fruit the Spirit produces in a believer’s life.
* It is an evidence of the newness of life we enjoy in Christ. [John 3:3]
* It is a testament of how much we need God and what He’s done for us.

[16]You can detect them by the way they act, just as you can identify a tree by its fruit. You need never confuse grapevines with thorn bushes or figs with thistles.
[17]Different kinds of fruit trees can quickly be identified by examining their fruit.
[18]A variety that produces delicious fruit
– Matthew 7:16-18

Having done a contextual analysis of what the fruit of the spirit is, we come to manifestation of the fruit we are focused on. “Faithfulness”.
As it has been said concerning the fruit that they are the character of God. And this is one which we are very familiar with. I.e we many times refer to the faithfulness if God. [Psalm 36:5, 89:1-2,5]. This He has shared with us to be a part of us, something that naturally comes to us through the Spirit. We can define Faithfulness as the manifestation of the fruit of Spirit which that pertains to loyalty and trustworthiness. As believers we have been called to work and walk with a God who is loyal and Trustworthy, to effectively walk with Him we need to imbibe thus trait of His. It is God’s desire that we’ll look like Him.
Faithfulness is a requirement for every servant of Christ. So look at Apollos and me as mere servants of Christ who have been put in charge of explaining God’s mysteries. Now, a person who is put in charge as a manager must be faithful.
[Corinthians 4:1-2] if we must be effective in our service to God it is a requirement we can’t do without. And God has graciously equiped us through His Spirit. But when we try to do it by our own strength, it is counted as debt l, but when done by grace through the Spirit it is to our commendation.

For what does the Scripture say? “Abraham believed God, and it was accounted to him for righteousness.” Now to him who works, the wages are not counted as grace but as debt. But to him who does not work but believes on Him who justifies the ungodly, his faith is accounted for righteousness.

– Romans 4:3-5

*In the kingdom of God, God does not reward based on How big or long our service is but He rewards faithfulness [Matthew 20:1-16]
The fruit of the spirit is the very character of Christ been manifested in us. We can say that all the various manifestation of the fruit of the Spirit leads to faithfulness because at the end of it all if we posses and manifest all of the different seeds of the Spirit and lack faithfulness, we will loose out of His Kingdom because every other manifestation leads to faithfulness.
[Matthew 24:45-51].

* Faithfulness makes God commit into our hands the things of the kingdom and also is a basis for more [Matthew 25:21]. When we show God that we are loyal to Him and Worthy if His trust.
Through our yieldedness to His Spirit to work in us and through us even in little things, He opens to us greater and deeper dimensions in our walk and work with Him and He entrust into our hands bugger responsibility.

* Faithfulness brings us into the joy of the Lord [Matthew 25:21]
One manifestation of the fruit of the Spirit is Joy which surpasses Happiness and is also a character of God and comes from the presence of God and total obedience and reliance upon the Lord.

The joy of the Lord has been promised to all children of God, unlike the temporary Happiness the world offers or portrays which is based on circumstances and the present pleasant happening but the Joy of the Lord comes from a place of total dependency and trust in God yo deliver on the hope that has been promised. And only faithfulness proves us Worthy to be brought into this joy and not just that , but we share in the joy of our Lord.

* Faithfulness empowers to the death.

“Do not fear any of those things which you are about to suffer. Indeed, the devil is about to throw some of you into prison, that you may be tested, and you will have tribulation ten days. Be faithful until death, and I will give you the crown of life.”
– Revelation 2:10

Although we don’t like to to talk about death. We have been called to die to the flesh and it’s deeds and many times we seem to want to return to this old way in which we have been dead to to. Faithfulness to the call and cause of the Spirit empowers us to die daily and even when it is required of us to die physically as a result of our faith, faithfulness empowers us to the very death as a testimony of our trust in God, for our victory over death.

I have been crucified with Christ; it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me and gave Himself for me.

– Galatians 2:20

* Faithfulness gets us the crown of Life [Rev 2:10] although it empowers us to die it is also a testimony of all that we have been through as a result of our faith and gets us the crown of Life.

In conclusion, just as every manifestation of the fruit of the spirit, this are characters that builds up with time in a believer’s life. This manifestation is a testament to how we have been obedient and loyal to the precepts and instructions of God even when it doesn’t seem like the best thing to do.
We must also note that faithfulness only comes through trials, tests and temptation, and can be said to be a character biult in us us overtime and a testimony of how we have overcome through total dependence and loyalty to God’s precepts and commands