We can get the false impression that this was the first life in which Yogananda found God, but our line of gurus has been coming around for a long time. Yogananda said that in a former lifetime Lahiri Mahasaya was King Janaka, one of the great sages of ancient India. Babaji was Krishna. Yogananda also said that Babaji, Lahiri, and Sri Yukteswar were the three wise men.
There is a great difference between an ordinary master and an avatar such as Yogananda. A master still must free himself from this body but an avatar is already free. A master can free maybe six people, maybe a few more. An avatar has the power to bring thousands, perhaps millions to God.
In Autobiography of a Yogi, Yogananda’s mother brought him as a babe in arms to Lahiri Mahasaya for his blessing. When Lahiri saw him, he said, “Little mother, thy son will be a yogi. As a spiritual engine, he will bring many souls to God’s kingdom.”
What does an engine do? It draws many cars of people behind it. Lahiri meant that Yogananda had the kind of power that would distinguish him as an avatar. These are esoteric statements that you won’t catch with a casual reading, but if you look for subtler meaning, you’ll see what a powerful statement this is.