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.

1950. 'His hand will be against all' means that it will fight against those things that are not true, and 'the hand of all against him' means that falsities will fight back. This is clear from the fact that 'Ishmael', as has been stated, means rational truth separated from good; and when it is said, referring to this truth, that 'his hand will be against all and the hand of all against him', it is clear that such is the meaning of these words. It has been shown above that 'Abram' represents the Lord's Internal Man, or what amounts to the same, His Divine Celestial and Spiritual; 'Isaac' the Lord's Interior Man, or His Divine Rational; and 'Jacob' the Lord's Exterior Man, or His Divine Natural. Described here is the nature of the rational if it were not united to the Internal Man, or Divine Celestial and Spiritual. Because the rational derived its nature from the life belonging to the affection for knowledge, that is, from Hagar, Sarai's Egyptian servant-girl, and because that life belonged to the external man and possessed a heredity from the Lord's mother which had to be fought against and cast out, the nature of the rational if devoid of rational good is therefore described. But after the Lord had humbled, or afflicted and subdued, that heredity by means of conflicts brought about by temptations, and by victories, and He had with Divine good brought life to the Rational itself, the latter at that point became Isaac, that is, it is represented by Isaac, after Ishmael has been cast out of the house together with Hagar his mother.

[2] The whole of the genuine rational consists of good and truth, that is, of what is celestial and what is spiritual. Good or what is celestial is its actual soul or life, truth or what is spiritual is that which draws its life from that good. A rational devoid of life received from celestial good is as is described here, that is to say, it fights with all, and all fight with it. Rational good never fights, no matter how much it is assailed, because it is gentle and mild, long-suffering and yielding, for its nature is that of love and mercy. But although it does not fight, it nevertheless conquers all. It does not ever think of combat, nor does it glory in victory. It is of this nature because it is Divine and is of itself immune from harm; for no evil can assail good, indeed it cannot even remain in the sphere where good is. Just as soon as it approaches, evil retreats of itself and falls back; for evil is of hell, while good is of heaven. Much the same is the case with that which is celestial-spiritual, that is, with truth from a celestial origin, or truth that derives from good, for such truth is truth formed from good - insomuch that one may call it the form of good.

[3] But truth separated from good, which is represented here by Ishmael and is described in this verse, is altogether different, for it is like a wild ass, fighting with all and all with it. Indeed it hardly does anything else than think about and long for conflict. Its general delight or ruling affection is conquest, and when it conquers, it glories in victory. This is why it is described as a wild ass, that is, as a mule living in the wilderness or an ass in the wild, that is unable to live with others. A life such as this is what the life of truth devoid of good is like, and indeed what the life of faith devoid of charity is like. When therefore a person is being regenerated the regeneration is achieved, it is true, by means of the truth of faith, yet it is being achieved at the same time by means of the life of charity which the Lord instills in proportion to the increases in the truths of faith.