First-Begotten; First-Born

Boyd’s Bible Dictionary:

Consecrated to God
(Ex. 13:2); received a double portion (Deut. 21:17). Paid redemption money after the priesthood started (Num. 3:12-13; 18:15-16).

Concise Bible Dictionary:

1. Moses was to say to Pharaoh, "Thus saith the Lord, Israel is My son, even my first-born" (Ex. 4:22). God called him out of Egypt, which is applied also to the Lord Jesus (Hos. 11:1; Matt. 2:15).
2. Because Pharaoh refused to let God's first-born go, all the first-born of Egypt were slain (Ex. 12:29).
3. God claimed for Himself all the first-born of the children of Israel, and of their cattle. The first-born of Israel were redeemed by the sons of Levi, as far as they went, and the remainder were redeemed with money (Num. 3:12-51).
4. To the first-born son in a family pertained the birthright. Esau was called a profane person for selling his birthright: it was despising the gift of God. The first-born son was to inherit a double portion of his father's property (Deut. 21:15-17).
5. In the N. T. the term is applied to the Lord: He was Mary's first-born (Matt. 1:25). He is also called, in pre-eminence, “the first-born of every creature” (Col. 1:15); “the first-born among many brethren” (Rom. 8:29); and “the first-born from the dead” (Col. 1:18; Rev. 1:5). In bringing “the first-begotten” into the world, God says, "Let all the angels of God worship him" (Heb. 1:6).
In the O. T. also the title had the force of pre-eminence, irrespective of the time of birth. David, though the youngest, was made the firstborn: (Compare Psalm 89:27). Christ also in every relationship must have the first place, as is manifest in the above passages.

From Anstey’s Doctrinal Definitions:

This term is used in Scripture in two ways:
•  To denote those who are born first in a family—birth order.
•  To denote those who are first in rank and position, having a place of preeminence among others.
Some examples of the two ways in which the term is used in the Old Testament are:
ISAAC’S SONSEsau was born first (Gen. 27:19), but Jacob (Israel) was given the place of preeminence as “firstborn” (Ex. 4:22).
JACOB’S SONS—Rueben was born first (Gen. 46:8), but Judah was chosen to have the royal lineage (Gen. 49:8; 1 Chron. 5:1-2).
JOSEPH’S SONS—Manasseh was first in birth order (Gen. 41:51; 48:14), but Ephraim was given the place of being first in rank as “firstborn” (Jer. 31:9).
JESSE’S SONS—Eliab was first in birth order (1 Chron. 2:13-15), but David was given the place of preeminence as “firstborn” (Psa. 89:27).
THE LORD JESUS CHRISTHe was born first in Joseph and Mary’s family (Matt. 1:25; Luke 2:7) and He is also set in the first place, in rank and position, in everything in connection with the purpose of God (Rom. 8:29; Col. 1:15, 18; Heb. 1:6; Rev. 1:5). Thus, He is “Firstborn” in both ways.
Colossians 1:15 says that He is “the Firstborn of all creation.” Being the Creator of the universe (John 1:3, etc.), when He came into the world (His incarnation), He could have no other place than that of Head of His own creation. Being the Firstborn among His creatures distinguishes Him as having a superior place to them. Colossians 1:18 indicates that the Lord is Firstborn in another way. When He rose “from among the dead,” He became the “Firstborn” of a whole new race of men (Rom. 8:29 – “many brethren”). Since they are of the same “kind” as He is in new creation (compare Gen. 1:24), they are entirely suited to be His eternal companions, and thus “He is not ashamed to call them brethren” (Heb. 2:11). As “the Firstborn from the dead,” the Lord Jesus is the triumphant Redeemer who now has the right to receive the saints’ praise and worship (Rev. 1:5-6). Revelation 1:5 indicates that the Lord as “Firstborn” has the title and right to take the inheritance (every created thing) and to reign over it, which He will do at His Appearing (Rev. 1:7). (Hebrews 1:6, in the KJV says “First-begotten,” but it should be translated “Firstborn.”)
As “Firstborn,” the Lord has many brethren under Him in His new creation race (Rom. 8:29), but as the “Only-begotten,” there are no brethren connected with Him because that term denotes divine essence, which no creature can have or will ever reach. (See Only-begotten.)
THE CHURCH OF GOD—The term is also applied to the Christians. In the Greek manuscripts it is in plural, and is translated by W. Kelly as “firstborns [firstborn ones]” to indicate it (Heb. 12:23). This shows that those who have been called by the gospel today, and thus are part of the Church of God, have been set in a special and favoured place among all of God’s blessed creatures in His family (Eph. 3:15). They have a superior place in the family of God—even above angels—with superior blessings that correspond with their privileged place! It is not that they are better than the others in the family, but because God has purposed to display “the glory of His grace” through them (Eph. 1:6). He has taken the lowest of men and through grace has set them in the highest possible place of blessing. (See Adoption.)