Deuteronomy 7:22

The Lord your God will clear away these nations before you little by little; you will not be able to put an end to them quickly, for [if you did] the wild animals would become too numerous for you.

Exodus 23:29-30

I will not drive them out before you in a single year, so that the land does not become desolate [due to lack of attention] and the [wild] animals of the field do not become too numerous for you.

Joshua 15:63

But as for the Jebusites, the inhabitants of Jerusalem, the [tribe of the] sons of Judah were not able to drive them out; so the Jebusites live with the sons of Judah in Jerusalem to this day.

Treasury of Scripture Knowledge

Summary

And the LORD thy God will put out those nations before thee by little and little: thou mayest not consume them at once, lest the beasts of the field increase upon thee.

General references

Bible References

Thou mayest

Exodus 23:29
I will not drive them out before you in a single year, so that the land does not become desolate [due to lack of attention] and the [wild] animals of the field do not become too numerous for you.
Joshua 15:63
But as for the Jebusites, the inhabitants of Jerusalem, the [tribe of the] sons of Judah were not able to drive them out; so the Jebusites live with the sons of Judah in Jerusalem to this day.

General references

Deuteronomy 11:23
then the Lord will drive out all these nations from before you, and you shall dispossess nations greater and mightier than you.
Joshua 21:44
The Lord gave them rest [from conflict] on every side, in accordance with everything that He had sworn to their fathers, and not one of all their enemies stood before them [in battle]; the Lord handed over all their enemies to them.