The first altar mentioned in the Word was the one built by Noah after he came out of the ark, after being saved from the great flood. On that altar, he sacrificed clean animals to the Lord.

Mountains represent the Lord because of their height; we need to raise our thoughts above worldly things when "talking" with the Lord. An altar is a small artificial mountain. When it's used in worship, it can call to mind this raising of thought. The fire and smoke that rise from an altar are symbolically being sent to the Lord.

Most altars were made from unhewn stones. Stones represent truths. Unhewn stones - ones that have not been shaped by men - represent truths from the Word, truths that have not been adulterated.

The clean beasts to be sacrificed represent good things, charitable acts done because they are right. The clean birds represent thoughts about doctrine and actions, and about what is right. Presenting these things is an acknowledgment that we have them from the Lord, and a giving thanks to Him for them.

In the Israelitish Tabernacle, the altar of burnt offering represented the acknowledgment of good and the altar of incense that of truth. For this reason this larger altar, which was outside by the door, was made of brass which signifies natural good, while the altar of incense was made of gold, which signifies love to the Lord from whom comes truth.

6637. 'These are the names of the children of Israel' means the essential nature of the Church. This is clear from the meaning of' the name as the essential nature, dealt with in 144, 145, 1754, 1896, 2009, 2628, 2724, 3006, 3421; from the representation of 'the sons of Israel' as spiritual truths, dealt with in 5414, 5879, 5951; and from the representation of 'Israel' as the good of truth, which is spiritual good, dealt with in 3654, 4598, 5803, 5806, 5812, 5817, 5819, 5826, 5833. Since Israel' represents the good of truth or spiritual good and 'his sons' represent spiritual truths in the natural, 'the sons of Israel' also represent the Church, for what makes it the Church is spiritual good and the truths that spring from that good. A person without spiritual good, that is, the good of charity, and without spiritual truths, that is, the truths of faith, does not belong to the Church in spite of having been born within the Church. The whole of the Lord's heavenly kingdom possesses the good of love and faith, and unless the Church possesses good like that it cannot be the Church since it is not joined to heaven; for the Church is the Lord's kingdom on earth.

[2] The term 'Church' is not used because it is the place where the Word is and teachings drawn from it, or because it is where the Lord is known and the sacraments are celebrated. Rather it is the Church because it lives in accordance with the Word or with teachings drawn from the Word, and seeks to make those teachings its rule of life. People who do not live like this do not belong to the Church but are outside it; and those who lead wicked lives, thus lives contrary to that teaching, are further away outside the Church than gentiles who know nothing whatever about the Word, the Lord, or the sacraments. For since those people are acquainted with the forms of good that the Church fosters and with the truths it teaches they annihilate the Church within themselves, something gentiles cannot do because they are unacquainted with those things. It should also be realized that everyone who leads a good life, in charity and faith, is a Church, and is a kingdom of the Lord. He is for that reason also called a temple, and a house of God too. Those who are Churches individually, no matter how remote from one another they may be, constitute one Church collectively. This then is the Church meant by the expression 'the children of Israel' here and in what follows.