Genesis 21:33

And he planted a garden, (lit., "a paradise,") at the Well of the Seven Lambs, and prepared in the midst of it food and drink for them who passed by and who returned; and he preached to them there, Confess ye, and believe in the Name of the Word of the Lord, the everlasting God.

AND HE CALLED THERE IN THE NAME OF THE ETERNAL, ‘E-IL OLAM’ (THE EVERLASTING G-D). Scripture explains that Abraham called by the name Eternal He Who in His might directs the time.
It may be that heaven and earth are here being called olam (world) [so that the sense of the verse is, “he called by the name Eternal the G-d of the world”], as is a customary expression in the words of our Rabbis. Thus Scripture informs us by this that Abraham called out and informed people of the secret of the leadership of the entire world, namely, that it is in the name of the Eternal, the Mighty One in strength, Supreme in power over all.
Now the Rabbi, Note 139. said in the Moreh Nebuchim that this alludes to the principle of the pre-existence of G-d since Abraham let it be known that G-d existed before the creation of time. Onkelos, however, said of the word vayikra (and he called), that it refers to prayer.

ויטע אשל, an orchard. The presence of such an orchard should encourage people to pray to G’d there.

ויקרא שם בשם ה' א-ל עולם, he used the occasion to proclaim the eternal nature of G’d, as opposed to any other deities, which, even if on occasion appearing to have demonstrated some power to protect those worshipping them, could at best enjoy a brief period of effectiveness.

ויטע אשל, he planted some saplings there to serve as proof that the well nearby was now his undisputed property. The word אשל describes certain plants (fruit-bearing) as In Samuel I 22,6 תחת האשל ברמה, “under the eshel in Ramah). According to our sages in Beytzah 27 the reference is to tall trees which are difficult to uproot. Our sages in Midrash Tehillim 110 understand the word אשל as an acronym for אכילה, שתיה, לינה, “eating, drinking, staying overnight.” In other words, Avraham established a hotel there to serve people passing that region. He taught the people around Beer Sheva to practice the art (virtue) of hosting strangers. In order to fulfill that virtue one must provide the three ingredients represented by the three letters in the word אשל.

ויקרא שם, Avraham used the opportunity of assembling the local people and describing his and Sarah’s experiences to them in order to give them first-hand evidence of how G’d had looked after him against all odds. He contrasted this with the local deities being worshipped who could not protect those who sacrificed to them.
א-ל עולם, he pointed out that his G’d was not only powerful locally, but was a G’d Who was equally powerful allover the globe, seeing the globe is His, He being the One Who had created it.