Thou preparedst room before it - The Hebrew word used here means properly to turn; to turn the back; then, to turn in order to look at anything; to look upon; to see; then, in Piel, to cause to turn away; to remove. Then it comes to mean to remove, or to clear from impediments so as to prepare a way Isaiah 40:3; Isaiah 57:14; Isaiah 62:10; Malachi 3:1, and hence, to remove the impediments to planting a vine, etc.; to wit, by clearing away the trees, brush, stones, etc. Compare Isaiah 5:2. Here it means that the hindrances in planting the vine were taken out of the way; that is, God removed the pagan so that there was room then to establish his own people.
And didst cause it to take deep root - Hebrew, “And didst cause it to root roots;” that is, Its roots struck deep into the soil, and the plant became firm.
And it filled the land - Its branches ran everywhere, so as to fill the whole land. See the notes at Isaiah 16:8.