If you believe "God demonstrates his own love for us in this: While we were still sinners, Christ died for us."Romans 5:8, you can say I have faith
Faith is believing in the love of God. Not that I loved him first, but he loved me and gave himself for me. Believing in this love is faith.
Direct answer:
Hebrews 11:1-6 New International Version (NIV)
11 Now faith is confidence in what we hope for and assurance about what we do not see. 2 This is what the ancients were commended for.3 By faith we understand that the universe was formed at God’s command, so that what is seen was not made out of what was visible.
4 By faith Abel brought God a better offering than Cain did. By faith he was commended as righteous, when God spoke well of his offerings. And by faith Abel still speaks, even though he is dead.
5 By faith Enoch was taken from this life, so that he did not experience death: “He could not be found, because God had taken him away.” For before he was taken, he was commended as one who pleased God. 6 And without faith it is impossible to please God, because anyone who comes to him must believe that he exists and that he rewards those who earnestly seek him.
The whole of chapter 11 of Hebrews (New Testament) describes faith fully.