(a)  Romans 8:5 they that are after the flesh do mind the  things of the flesh
"That which is born of the flesh is flesh; and that which is born of the Spirit is spirit." (John 3:6)
"But  the natural man receiveth not the things of the  Spirit  of God:  for  they  are foolishness unto him: neither  can  he  know [them],  because they are spiritually discerned." (1  Corinthians 2:14)