The New Testament has a definite affirmative answer to this question in the first epistle of John chapter 4:7 "Whoever loves is born of God, and he who does not love does not know God." The definitive evidence that you have faith in God is that you have the love of God. The definition of faith would be deficient if we do not pay attention to the words of St Paul in his epistle to the Galatians chapter 5 :6 " the faith which works by love." In the sense that faith is not faith if it is not fruitful, and the fruit is the life of love. Jesus said that it is by our fruits that we are known as His disciples (Mathew 7:20) “Thus you will recognize them by their fruit”. Fruitless branches—professing believers who do not display the fruit of the Spirit are cut off ( John 15:6) ”If anyone does not abide in me he is thrown away like a branch & withers” . A genuine faith is one that not only believes in God, the devils themselves do that, but leads to obedience to Christ's commands, (James 2:19) “You believe that God is one; you do well. Even the demons believe & shudder!”. Faith should be activated and expressed through love.
St. Paul in his epistle to the Romans chapter 10 :9 said “ Say with your mouth,” Jesus is Lord”. Believe in your heart that God raised him from the dead. Then you will be saved.” The word “in your heart” here means your love, in other words, if you have the faith that produces love. So St. Paul made sure that faith is not a word said with your mouth and your tongue, but to be seen in you the fullness of Jesus’ love that you have believed in and loved from your heart. And St. Paul completes the verse and says that this love that you have received from your faith in Christ, is the sign of your acceptance of Christ and your unity with Him, which is also the sign that you are saved.
Salvation is the unity with Christ. This love and faith in Jesus is not just a human feeling and emotion, but the love that proves your faith in him, as Jesus defined it in the Gospel of John chapter 14:21 “ Anyone who has my commands and obeys them loves me.” So the faith in Jesus is the faith that leads you to love. And the proof and sign of this love is your obedience to His commandments. So this is the faith that will save you. Now we can summarize and say that the proof of you having faith in God, is the love in you. And the sign of your salvation is that this love has a fruit in your life.