How we cite our quotes: (Part.Chapter.Paragraph)
Quote #4
Lara was not religious. She did not believe in rites. But sometimes, in order to endure life, she needed it to be accompanied by some inner music. (2.17.1)
As we find out, Lara isn't a religious person. But at the same time, she's not happy with living in a world that's cold and indifferent to human suffering. She needs for there to be something spiritual (or "musical"—music is often a metaphor for spirituality in literature) beneath the world around her, even if it's not hard-and-fast religion, per se.
Quote #5
The soul of these books was a new understanding of Christianity, their direct consequence a new understanding of art. (3.2.10)
Zhivago's uncle Nikolai isn't a modest thinker. He plans on writing books that'll totally change people's understanding of Christianity, and through it, a new understanding of art. Or in other words, changing the way you look at Christianity can change the way you look at the whole world, especially the way it's presented to you through art. This is another way in which art and spirituality are linked in the book.
Quote #6
"But it said: in that new way of existence and new form of communion, conceived in the heart and known as the Kingdom of God, there are no people, there are persons." (4.12.14)
In this passage, we find Nikolai Nikolaevich arguing that the truly revolutionary thing about Christianity is the way it honors the power of individuals instead of groups. In other words, it's about persons more than people. Christ himself was an individual, and he managed to change the whole world. Hundreds and thousands of people tried to stop him, but the individual triumphed in the end.