Catechism of the Catholic Church 2546
“Blessed are the poor in spirit.” (Mt 5:3.) The Beatitudes reveal an order of happiness and grace, of beauty and peace. Jesus celebrates the joy of the poor, to whom the Kingdom already belongs.
“The Word speaks of voluntary humility as ‘poverty in spirit’; the Apostle gives an example of God’s poverty when he says: “For your sakes he became poor.” (St. Gregory of Nyssa, De beatitudinibus 1:PG 44,1200D; cf. 2 Cor 8:9.)