"Jesus prayed and did not pray in vain, since he received what he asked for in prayer when he might have done so without prayer. If so, who among us would neglect to pray? Mark says that 'in the morning, a great while before day, he rose and went out to a lonely place, and there he prayed.' And Luke says, 'He was praying in a certain place, and when he ceased, one of his disciples said to him, 'Lord, teach us to pray,' and elsewhere, 'And all night he continued in prayer to God.' And John records his prayer, saying, 'When Jesus had spoken these words, he lifted up his eyes to heaven and said, 'Father, the house has come, glorify your Son that the Son may glorify you.' The same Evangelist writes that the Lord said that he knew 'you hear me always.' All this shows that the one who prays always is always heard."
Origen, On Prayer