What the Bible says about Ger
(From Forerunner Commentary)
The Hebrew language lacks an exact equivalent to the Greek noun proselyte, which means a newcomer (Strong's #4339). However, in the Old Testament, God's law does allow the ger (Strong's #1616), usually rendered "stranger," to become a full-fledged citizen of Israel. To do this, he needed to become circumcised. Exodus 12:48 addresses this changing of belief system in reference to the Passover.
The stranger "wants to keep the Passover." There is no hint of God expecting Israel to seek converts among the heathen by actively preaching to—or, at—them. Here, there is no coercion, subtle or otherwise; the Gentile convert voluntarily gives himself to come under the Old Covenant. Deuteronomy 4:5-7 states the dynamics of this conversion.
Charles Whitaker
Proselytism Yesterday, Today, and Tomorrow (Part One)