"The followers of Christ were instructed not to pray for the purpose of being heard of men. “But thou, when thou prayest, enter into thy closet, and when thou hast shut thy door, pray to thy Father which is in secret; and thy Father which seeth in secret shall reward thee openly” ( Matthew 6:6 ). Such expressions as this from the lips of Christ show that He did not regard with approval that kind of piety so prevalent among the Pharisees. His teachings upon the mount show that deeds of benevolence assume a noble form and acts of religious worship shed a most precious fragrance when performed in an unpretending manner, in penitence and humility. The pure motive sanctifies the act. SL 8.4"
"But thou, when thou prayest, enter into thy closet, and when thou hast shut thy door, pray to thy Father which is in secret; and thy Father which seeth in secret shall reward thee openly."
Ellen White directly references Matthew 6:6 in this passage.