Abraham put his faith in YAHWEH by believing that HE would fulfill HIS promise to give him and Sarah a son in their old age and make their seed great which was fulfilled in the life of our Lord and Savior YAHSHUA (JESUS). Abraham and Sarah were rewarded for their faith in YAHWEH’s promise.
Genesis 12:1-4 Now the LORD had said unto Abram, Get thee out of thy country, and from thy kindred, and from thy father’s house, unto a land that I will shew thee: and I will make of thee a great nation, and I will bless thee, and make thy name great; and thou shalt be a blessing: and I will bless them that bless thee, and curse him that curseth thee: and in thee shall all families of the earth be blessed. So Abram departed, as the LORD had spoken unto him; and Lot went with him: and Abram was seventy and five years old when he departed out of Haran.
Hebrews 11:1-13 Now faith is the assurance (title deed, confirmation) of things hoped for (divinely guaranteed), and the evidence of things not seen [the conviction of their reality—faith comprehends as fact what cannot be experienced by the physical senses]. For by this [kind of] faith the men of old gained [divine] approval. By faith [that is, with an inherent trust and enduring confidence in the power, wisdom and goodness of God] we understand that the worlds (universe, ages) were framed and created [formed, put in order, and equipped for their intended purpose] by the word of God, so that what is seen was not made out of things which are visible. By faith Abel offered to God a more acceptable sacrifice than Cain, through which it was testified of him that he was righteous (upright, in right standing with God), and God testified by accepting his gifts. And though he died, yet through [this act of] faith he still speaks. By faith [that pleased God] Enoch was caught up and taken to heaven so that he would not have a glimpse of death; and he was not found because God had taken him; for even before he was taken [to heaven], he received the testimony [still on record] that he had walked with God and pleased Him. But without faith it is impossible to [walk with God and] please Him, for whoever comes [near] to God must [necessarily] believe that God exists and that He rewards those who [earnestly and diligently] seek Him. By faith [with confidence in God and His word] Noah, being warned by God about events not yet seen, in reverence prepared an ark for the salvation of his family. By this [act of obedience] he condemned the world and became an heir of the righteousness which comes by faith. By faith Abraham, when he was called [by God], obeyed by going to a place which he was to receive as an inheritance; and he went, not knowing where he was going. By faith he lived as a foreigner in the promised land, as in a strange land, living in tents [as nomads] with Isaac and Jacob, who were fellow heirs of the same promise. For he was [waiting expectantly and confidently] looking forward to the city which has foundations, [an eternal, heavenly city] whose architect and builder is God. By faith even Sarah herself received the ability to conceive [a child], even [when she was long] past the normal age for it, because she considered Him who had given her the promise to be reliable and true [to His word]. So from one man, though he was [physically] as good as dead, were born as many descendants as the stars of heaven in number, and innumerable as the sand on the seashore. All these died in faith [guided and sustained by it], without receiving the [tangible fulfillment of God’s] promises, only having seen (anticipated) them and having welcomed them from a distance, and having acknowledged that they were strangers and exiles on the earth.