Father Vincent is a young, "rosy-cheeked" (1.11.7) English priest who lives at the Mission House with Msimangu. (We're emphasizing that he's rosy-cheeked because that is how is described when he first appears in chapter 5, before we learn his name in chapter 11.) He and Kumalo exchange life stories over dinner, as Father Vincent talks about "the hedges and the fields, and Westminster Abbey" (1.11.7).
Side note: Westminster Abbey is a big Gothic church in the city of London; it's where the kings and queens of England get crowned. The fact that Father Vincent specifically mentions somewhere as iconic as Westminster Abbey indicates that he's supposed to be super-, almost stereotypically, English. Since he's English, and not South African, it makes sense that his racial politics might be a bit different from some of the other white characters in the novel.
Father Vincent is a generous, liberal man who wants to understand Kumalo and where he comes from. He also introduces Kumalo to Mr. Carmichael, a lawyer who is willing to take Absalom's case for free because it is the right thing to do. So Father Vincent is genuinely a great help to Kumalo. Sounds like a good dude all around right?
Well, it's a bit more complicated than that. See, Father Vincent also provides an example of what we mean when we say that Cry, the Beloved Country can get a little bit "paternalistic." Paternalism means interfering in someone else's life as though you are their father. Someone who is being paternalistic might mean well when they try to manage another person's business, but they don't always see how their help might appear high-handed, and might not be all that welcome.
So, when Kumalo angry and distressed after visiting Absalom in prison for the first time, Father Vincent advises him:
[D]o not pray for yourself, and do not pray to understand the ways of God. For they are secret […] Pray for your wife and all at Ndotsheni. Pray for the woman and the children that are bereaved. Pray for the soul of him who was killed, and for those at Ezenzeleni, who try to rebuild in a place of destruction. Pray for your own rebuilding. Pray for all white people, those who do justice, and those who would do justice if they were not afraid. And do not fear to pray for your son, and for his amendment. (1.15.70)
Of course, as a spiritual advisor, it makes sense that Father Vincent talks to Kumalo with some authority. When he tells Kumalo not to "pray to understand the ways of God," because the ways of God are beyond human knowledge, that's consistent with Christian faith. But some readers might find Father Vincent's instructions to his fellow priest Kumalo on whom to pray for kind of condescending: surely the man can decide his own prayers? He is a reverend after all.
Nonetheless, Father Vincent's particular instructions are totally consistent with the novel's message of universal love. By telling Kumalo to pray, not only for his own people, but also for "all white people" who might try to improve the social conditions of South Africa "if they were not afraid," Father Vincent is reminding Kumalo not to let himself get carried away with resentment towards either his own son (who has gotten himself into so much trouble) or towards the white society that has made Absalom's life so hard.