4 Now those who do not observe the feast, continue such as these even to the present day, feigning indeed and devising names of feasts, but rather introducing days of mourning than of gladness; 'For there is no peace to the wicked, says the Lord.' And as Wisdom says, 'Gladness and joy are taken from their mouth. ' Such are the feasts of the wicked. But the wise servants of the Lord, who have truly put on the man which is created in God, have received gospel words, and reckon as a general commandment that given to Timothy, which says, 'Be an example to the believers in word, in conversation, in love, in faith, in purity.'
So well do they keep the Feast, that even the unbelievers, seeing their order, may say, 'God is with them of a truth.' For as he who receives an apostle receives Him who sent him, so he who is a follower of the saints, makes the Lord in every respect his end and aim, even as Paul, being a follower of Him, goes on to say, 'As I also of Christ.' For there were first our Saviour's own words, who from the height of His divinity, when conversing with His disciples, said, 'Learn of Me, for I am meek and lowly in heart, and you shall find rest to your souls.'
Then too when He poured water into a basin, and girded Himself with a towel, and washed His disciples' feet, He said to them, 'Know what I have done. You call Me Master and Lord, and you say well, for so I am. If therefore I, your Lord and Master, have washed your feet, you also ought to wash one another's feet: for I have given you an example, that as I have done to you, you also should do.'
Source: Letters (New Advent)