The supreme test of Abraham’s faith came about 20 years later. According to Jewish tradition, Isaac was now 25 years old. (Jewish Antiquities, by F. Josephus, I, 227 [xiii, 2]) In obedience to Jehovah’s instructions Abraham took Isaac and traveled N from Beer-sheba at the Negeb to Mount Moriah, situated directly N of Salem. There he built an altar and prepared to offer up Isaac, the promised seed, as a burnt sacrifice. And indeed Abraham “as good as offered up Isaac,” for “he reckoned that God was able to raise him up even from the dead.” Only at the last moment did Jehovah intervene and provide a ram as a substitute for Isaac on the sacrificial altar. It was, therefore, this implicit faith backed up by complete obedience that moved Jehovah to reinforce his covenant with Abraham with a sworn oath, a special legal guarantee.​—Ge 22:1-18; Heb 6:13-18; 11:17-19.

In Abraham’s time, the city of Ur was steeped in Babylonish idolatry and the worship of its patron moon-god Sin. (Jos 24:2, 14, 15) Nevertheless, Abraham proved to be a man of faith in Jehovah God, even as his forefathers Shem and Noah; and as a consequence, he earned the reputation “the father of all those having faith while in uncircumcision.” (Ro 4:11) Since true faith is based on accurate knowledge, Abraham may have received his understanding by personal association with Shem (their lives overlapped by 150 years). Abraham knew and used the name of Jehovah; to quote him: “Jehovah the Most High God, Producer of heaven and earth,” “Jehovah, the God of the heavens and the God of the earth.”​—Ge 14:22; 24:3.

While Abraham was still living in Ur, “before he took up residence in Haran,” Jehovah commanded him to move out to a strange land, leaving behind friends and relatives. (Ac 7:2-4; Ge 15:7; Ne 9:7) There in that country that He would show Abraham, God said he would make out of him a great nation. At the time, Abraham was married to his half sister Sarah, but they were childless and both were old. So it would take great faith to obey, but obey he did.

Sojourn in Canaan. Now 75 years old, Abraham began to move his household out of Haran to the land of Canaan, where he lived out the remaining hundred years of his life in tents as an alien and migratory resident. (Ge 12:4)

Here Jehovah appeared again to Abraham, confirming and enlarging His covenant promise by declaring: “To your seed I am going to give this land.” (Ge 12:7) Abraham not only built an altar to Jehovah there but, as he moved southward through the land, he built other altars along the way; and he called on the name of Jehovah. (Ge 12:8, 9) In time a severe famine compelled Abraham to move temporarily to Egypt, and to protect his life, he represented Sarah as his sister. This resulted in Pharaoh’s taking beautiful Sarah into his household to be his wife, but before he could violate her, Jehovah had Pharaoh give her back. Abraham then returned to Canaan to the campsite between Bethel and Ai and again called “on the name of Jehovah.”​—Ge 12:10–13:4.

When four allied kings, headed by the Elamite king Chedorlaomer, were successful in crushing a revolt of five Canaanite kings, Sodom and Gomorrah were sacked, and Lot was taken captive together with all of his property. Abraham, upon learning of this, quickly mustered 318 of his trained household servants. With his confederates Aner, Eshcol, and Mamre, he made a forced march in hot pursuit perhaps as much as 300 km (190 mi) northward to beyond Damascus and, with Jehovah’s help, defeated a far superior force. Lot was thus rescued, and the stolen property was recovered. (Ge 14:1-16, 23, 24) As Abraham was returning from this great victory a “priest of the Most High God,” Melchizedek, who was also the king of Salem, came out and blessed him, and Abraham, in turn, “gave him a tenth of everything.”​—Ge 14:17-20.

Appearance of the Promised Seed. Since Sarah continued to be barren, it appeared that Eliezer the faithful house steward from Damascus would receive Abraham’s inheritance. Nevertheless, Jehovah again reassured Abraham that his own offspring would become uncountable, as the stars of heaven, and so Abraham “put faith in Jehovah; and he proceeded to count it to him as righteousness,” even though this occurred years before Abraham was circumcised. (Ge 15:1-6; Ro 4:9, 10)

Indeed, this man of unusual faith walked with God, received communications from him by means of visions and dreams, and entertained his angelic messengers. (Ge 12:1-3, 7; 15:1-8, 12-21; 18:1-15; 22:11, 12, 15-18) He was well acquainted with the name of God even though Jehovah had not at that time revealed the full significance of His name. (Ex 6:2, 3) Time after time Abraham built altars and offered up sacrifices in the name of and to the praise and glory of his God Jehovah.​—Ge 12:8; 13:4, 18; 21:33; 24:40; 48:15.