Here are some quotations from Vladimir Lossky’s The Mystical Theology of the Eastern Church* which illustrate this idea.
Man, according to St. Basil, is a creature who has received a commandment to become God.
Man was created last, according to the Greek Fathers, in order that he might be introduced into the universe like a king into his palace.
God became man in order that man might become god, to use the words of Ireneus and Athanasius, echoed by the Fathers and theologians of every age.
* Vladimir Lossky, The Mystical Theology of the Eastern Church, James Clarke 1957, reprinted 1968. Quotations are taken, respectively, from pages 124, 111 and 134.