Genesis 21:33

“And [Abraham] planted a grove in Beersheba, etc.] The Jewish writers f1242 are divided about the use of this grove, as Jarchi relates; one says it was for a paradise or orchard, to produce fruits out of it for travellers and for entertainment; another says it was for an inn to entertain strangers in; it rather was for a shade, to shelter from the sun in those sultry and hot countries; and perhaps for a religious use, and to be an oratory, as the following words seem to suggest: in the midst of it very likely Abraham built an altar, and sacrificed to the Lord; hence might come the superstitious use of groves among the Heathens; and, when they came to be abused to idolatrous purposes, they…”

“Abraham planted a grove--Hebrew, "of tamarisks," in which sacrificial worship was offered, as in a roofless temple.”

“21:33-34 A tamarisk tree requires a lot of water; this act indicated Abraham’s security in his land rights and his faith that God would provide water in this desert area. He settled as a foreigner in the land, but dwelling under his tree was a sign of peaceful security (cp. Zech 3:10). • there he worshiped the Lord: See study note on 12:8.”