Here are some excerpts from Swedenborg's "Arcana Coelestia" that help explain the inner meaning of this chapter:

AC 3357. In the internal sense of this chapter the subject treated of is appearances of truth of three degrees, and how these were adjoined to truth Divine in order that truths and their doctrinal things might be received; and that a church might come into existence.

AC 3358. In (verses 1 to 6) are described the appearances of truth of a higher degree which are in the internal sense of the Word, in which appearances are the angels, and in which there is Divine truth and good. And that Divine good and truth cannot be comprehended, thus cannot be received, unless they are in appearances (verses 7 to 13).

AC 3359. Appearances of truth of a lower degree, which are in the interior sense of the Word-in which appearances those men may be who are of the internal church-are then treated of (verses 14 to 17).

AC 3360. Afterwards, appearances of truth are described of a still lower degree, which are of the literal sense of the Word, in which appearances those men may be who are of the external church (verses 18 to 25); and that through these there may still be conjunction with the Lord (verses 26 to 33).

AC 3361. Concerning truths of the memory adjoined to good therein (verses 34, 35).

3362. THE INTERNAL SENSE

Included in Chapter Genesis 21 is the description of a time when Abimelech made a covenant with Abraham, and when Abraham reproached him about a well of water that his servants had seized. Here a very similar description occurs again, involving Abimelech and Isaac, similar also in that, as Abraham had done, so also did Isaac call his wife his sister. From these considerations it is evident that the reason why similar events occurred again and are told again - with the mention of wells in both incidents - involves a Divine arcanum within it. Except for that which is Divine being concealed within them, there would be no value in knowing anything about those events. The internal sense however teaches what is concealed there and the fact that the subject is the Lord when joined to those who are in His Kingdom in heaven and on earth by means of truths - to angels by means of the appearances of truth belonging to a higher degree, and to men by the appearances of truth belonging to a lower degree, consequently by means of the Word where, in the internal sense and in the external sense, those appearances exist.

[2] For Divine truths are such that they cannot possibly be grasped by any angel, still less by any man. They go far beyond the whole range of their understanding. Yet so that the Lord may be joined to angels and men Divine truths flow in, with both angels and men, within appearances; and when those appearances have Divine truths within them, then these Divine truths can be received and acknowledged. And this is done in such a way as is adequate for everyone to grasp them. Appearances therefore, that is, angelic and human truths, exist in three degrees. These are the Divine arcana that are contained in the internal sense within the deeds done and told involving Abimelech and Abraham in Chapter 21, and these involving Abimelech and Isaac in this.