“The third Sunday of Great Lent is dedicated to the veneration of the life-giving Cross […] According to the ancient tradition of Constantinople, this was the Sunday at which catechumens preparing to be baptized on that Easter would be enrolled, accompanied by their sponsors. The Byzantine tradition has to this day preserved the practice of praying for ‘those preparing for illumination’ at a special litany added to the Presanctified Liturgy, following the litany for the catechumens, beginning in the week following the Sunday of the Cross.” (Archimandrite Job Getcha, The Typikon Decoded, p 191)
On the 3rd Sunday 0f Great Lent we read as our Gospel lesson Mark 8:34-9:1.
When He had called the people to Himself, with His disciples also, He said to them, “Whoever desires to come after Me, let him deny himself, and take up his cross, and follow Me. For whoever desires to save his life will lose it, but whoever loses his life for My sake and the gospel’s will save it. For what will it profit a man if he gains the whole world, and loses his own soul? Or what will a man give in exchange for his soul? For whoever is ashamed of Me and My words in this adulterous and sinful generation, of him the Son of Man also will be ashamed when He comes in the glory of His Father with the holy angels. And He said to them, “Assuredly, I say to you that there are some standing here who will not taste death till they see the kingdom of God present with power.”
Clement of Alexandria (d. ca 215AD) tells us to be a Christian is not only to take up the cross but also:
“For to truly follow the Savior is this: To aim at sinlessness and His perfection, to adorn and compose the soul before the mirror of Christ’s perfection, and to arrange everything in our lives to reflect that image.” (Clement of Alexandria, The One Who Knows God, p 30)