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.

9255. 'When you meet your enemy's ox or his ass going astray' means unauthentic good and unauthentic truth with those who are outside the Church. This is clear from the meaning of 'enemy' as those outside the Church, who are the subject below; from the meaning of 'ox' as the external man's good, and from the meaning of 'ass' as the external man's truth, both dealt with in 2781, 9135 - but unauthentic good and truth, such as exists with those outside the Church, who are meant by 'enemy'. The reason why those outside the Church are meant by 'enemy' is that they have a different idea of what the good and truth of faith are, because they do not possess the Word and therefore do not know anything about the Lord or about Christian faith and charity that come from the Lord alone. Consequently their truth of faith is not authentic, neither is their good of charity. Therefore also they do not live together in the next life with those who belong to the Church but are separated from them. All in the next life are formed into communities according to their good and the truth flowing from it, for these are what compose spiritual life and link people together.

[2] However, those in heaven do not regard people outside the Church as enemies; rather they teach them and bring them to Christian good, which is also welcomed by those of them who in the world have led dutiful and obedient lives, in some kind of charity towards one another that is prescribed by their religion. But the sense of the letter of the Word calls them 'enemies' on account of their lack of spiritual agreement, which is, as has been stated, their different idea of what the truth of faith and the good of charity are. See what has been shown from experience regarding the state and condition in the next life of nations outside the Church, in 2589-2604, 2861, 2863, 4190, 4197. The requirement to regard these very people as friends, and to teach and correct them, is the meaning in the internal sense of the words you shall surely bring it back, which the next paragraph deals with.

[3] Only this needs to be added here, that in the Word various kinds of beasts mean affections and inclinations such as the human being shares in common with beasts, and in the spiritual sense affections for goodness and truth, internal and external, see 45, 46, 142, 143, 246, 714, 715, 776, 2179, 2180, 2781, 3218, 3519, 5198, 9090; and that beasts were therefore used in sacrifices in accordance with their spiritual meaning, 1823, 2180, 2805, 2807, 2830, 3519. Consequently this law of personal conduct stating that an enemy's oxen and asses going astray should be brought back to him means in the spiritual sense such things as are characteristic of the Church, thus such as are feelings of mutual love or charity towards those whose ideas are different from the Church's truths.