And it came to pass at that time that Abimelech and Phichol, the commander of his army, spoke to Abraham, saying, “God is with you in all that you do". (Gen 21,22)
Abimelech first had a conflict with Abraham when he rebuked him for the way he had treated him (out of fear, Abraham concealed that Sarah was his wife, and when Abimelech took her into his harem, God scared him with a death threat if he has sex with her). From the above verse, we can better understand why Abraham was afraid at the time: "...and Phichol, the captain of his army." Abimelech was practically just a tribal leader of Gerar, but he also had his own army with a certain command structure, so it was not just a few people. When Abraham came to reside in their territory, he was clearly in the minority and acted accordingly in fear, but we've covered that before.
So, after God's intervention, Abimelech was afraid to harm Abraham, but his attitude towards him was certainly not entirely friendly. Rather, it could be described as "respect from a proper distance." But that is precisely why his observation that "God is with you, Abraham, in all that you do" is so valuable. If Abimelech had been his friend, he would have inclined to say only positive things to him and to view reality in a somewhat distorted way, as is usually the case with friends. At those we like we excuse a lot of things. But when a person who doesn't love us says something positive about us, then we can be sure it's true. So the Council of Constance senselessly condemned John Hus for heresies, but could not deny him (as it stated) that he lived a very virtuous life. Surely there can be no doubt about this, if even his enemies acknowledged it!
Abimelech's observation that God is with Abraham "in all things" demonstrates the extent of the greatness of God's blessing upon this man of God. Abimelech understood only that part of it which was outwardly visible, and could therefore reach the minds of the Gentiles. In other words, he measured God's favor by earthly success. He clearly seems not to have any idea of that far more precious part which is found in the inner man, when he is filled with a living relationship with God.
As for Abraham, I personally conclude that after his long road on the path of discipleship, this inner part was already much more important for him and far more valued.
