Heb. 11: 1-40
FAITH – BEING CERTAIN OF THE UNSEEN
“Now faith is being sure of what we hope for and certain of what we do not see.”  The “ancients” were all faithful to God for a salvation they could not see and did not understand, they were confident of what is unseen, and sure of what they hoped for. “By faith we understand…”  that God spoke, and everything that is now visible in the universe came into being, that what is now seen was not formed from what may have been visible, but from nothing!
“By faith Abel…” offered a better sacrifice than Cain. The contrast is between a careless, thoughtless choice and a generous offering; and here the attitude of giving to God is implied. God declares that Abel gave “in faith” as opposed to Cain, and God sees and knows the heart of the giver. Abel’s faith still “speaks” even though he is dead 
“Enoch… was commended as one who pleased God” Faith is the basis of any belief in God, and to accept the fact that God exists must be on the basis of faith. Faith must have an object, and the object of faith is God, He rewards the faith of those who earnestly seek Him. Without faith it is impossible to please God. 
“By faith Noah……” Warned of things not yet seen, he acted in faith and built an ark to save his family and when the flood came his faith was justified. By his faith he condemned the world and became an heir of righteousness. 
“By faith Abraham” When called by God obeyed and went even though he did not know where he was going and became a stranger in a foreign country. By faith he became a father (although impossible by human standards) because he considered God to be faithful to His promise. He offered Isaac in faith as a sacrifice (although God did not allow him to complete the act) because in faith he believed that God could raise Isaac back from the dead. 
Scripture References:  Heb. 11:1; 3:6; 2 Cor.4:18;  Heb. 11:3; Jn.1:3; Heb. 1:2; 2 Pet. 3:5;  Heb. 11:4; Gen. 4:3-4; Psa. 139:1-4, 23-24; Heb. 12:24;  Heb. 11:5-6; Jer. 29:13;  Heb. 11:7; 10:38;  Heb. 11:8-12, 17-19;  Heb. 11:20-22, 13;  Heb. 11:23-28;  Heb.11:29-37;  Heb. 11:38-40;  Heb. 11:13-16; Jn.11:25-26; Rev. 6:11; Heb. 2:10. – NIV