"Bartimaeus... a blind beggar, was sitting by the roadside" (Mark 10:46).

Mabel was a "blind, deaf, disease-ridden and cancerous" old lady of 89 whom the Christian writer Tom Schmidt once met in a convalescent home.

He asked her what she thought about as her body was ravaged by disease and the long days passed, and her response was striking: "I think about Jesus," she said. "I think about how good he's been to me. He's been awfully good to me in my life, you know... I'm one of those kind who's mostly satisfied." The incident is relayed in JI Packer's book A Passion for Holiness.

Mabel is an inspiring example of someone who, though physically blind, could see spiritual truths with 20/20 vision. But when we read the gospels we find that Jesus' disciples – perhaps like us – were rather slow to develop in this area. Indeed ironically, when we read Mark 10 we find that

 How come?

1. The disciples didn't see clearly that Jesus had to die, or why. Mark 10:33-34 finds Jesus explaining to his disciples – again – that he had come to die. Even though he had been through it with them a number of times previously, they had yet to grasp the centrality of the cross. And if we or those we care for are to develop 20/20 spiritual vision we and they need to develop a clear understanding of the cross and its necessity. For Jesus came "to give his life as a ransom for many" (verse 45).

2. The disciples didn't understand that following Jesus was about service, not status. Mark 10:35-37 tells us how James and John, two of Jesus' friends, seek the top spots in the kingdom he is ushering in. But they have got it completely wrong. "Grant us to sit, one at your right hand and one at your left," they demand. For them, faith was about what they could get out of it, including some prestige if at all possible. But Jesus makes it clear that "whoever wishes to be first... must be slave of all" (verse 44). It's all about service, and sacrifice – not status.

By contrast, the blind man, Bartimaeus, first encountered begging by the roadside, has clear spiritual sight.

1. The blind man saw clearly who Jesus is. He calls Jesus "Son of David" (verse 47) – a hugely significant Messianic title. The Old Testament had promised that the ultimate rescuer of humanity whom God would send would be a descendant of King David. So when people referred to Jesus as the Son of David, they meant that he was the long-awaited Deliverer, the fulfilment of the Old Testament prophecies. Bartimaeus had clearly grasped that.

2. The blind man saw clearly what he needed from Jesus. He didn't, unlike James and John, want status or prestige. He knew what he most needed. And so he calls out: "Jesus, Son of David, have mercy on me!" (verse 47). At the heart of 20/20 spiritual vision is the ability to see clearly what we most need – mercy, forgiveness and grace. Bartimaeus was granted his physical sight (verse 52) as a testament to his spiritual sight . As a result, we are told, he "followed Jesus on the way" – not only the physical road but the path of discipleship.

So how is your spiritual vision? How is your understanding of the cross? How much is your faith about what you can get out of it – or about how you can serve? Do you see clearly who Jesus is and what you most need?

Bishop JC Ryle in his famous commentary declares that, like Bartimaeus, "we too are not allowed to see Jesus with our bodily eyes". But, he continues, "What is the first step of a Christian, but a crying, like Bartimaeus, 'Jesus, have mercy on me'? What is the daily course of a Christian, but keeping up the same spirit of faith? Though now we see him not, yet believing, we rejoice."

And so we pray – using a version of the words of Bartimaeus popularised by the Eastern Orthodox Churches and known simply as The Jesus Prayer: "Lord Jesus Christ, Son of God, have mercy on me a sinner." Amen.

David Baker is a former daily newspaper journalist now working as an Anglican minister in Sussex, England. The Rough Guide to Discipleship is a fortnightly series.