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To be united to God in unity of person was not fitting to human flesh, according to its natural endowments, since it was above his dignity; nevertheless, it was fitting that God, by reason of his infinite goodness, should unite it to himself for human salvation.

St Thomas Aquinas (2013). “Summa Theologica, Volume 4 (Part III, First Section)”, p.2020, Cosimo, Inc.
To be united to God in unity of person was not fitting to human flesh, according to its natural endowments, since it was above his dignity; nevertheless, it was fitting that God, by reason of his infinite goodness,