וַיְהִ֕י כַּאֲשֶׁ֥ר שָׁמַ֛ע עֶ֥בֶד אַבְרָהָ֖ם אֶת־דִּבְרֵיהֶ֑ם וַיִּשְׁתַּ֥חוּ אַ֖רְצָה לַֽיהוָֽה׃
And it came to pass, that, when Abraham’s servant heard their words, he bowed himself down to the earth unto the LORD.
Rashi on Genesis
וישתחו ארצה HE PROSTRATED HIMSELF — From this we may learn that we should thank God for good news (Genesis Rabbah 60:6).
Radak on Genesis
ויהי..וישתחו ארצה, prostrating himself on the ground with arms and feet extended.
Haamek Davar on Genesis
And he prostrated towards the earth for God - Not just bending the knees, rather, he fell with his entire body to the land given his happiness and gratitude.