Christians often say like you Muslims we also fast. Tell them that's good to know, may I ask what are the principles and requirement of your fasting, how is fasting performed?
For example :
when do you start to fast and when do you cease to fast?
How many days are you to fast and what actions are taken whilst you fast?
What prayers are performed when you fast and end fast?
who decides what year month or day your fast to start and end? What are the conditions and actions of your fast?
Where did Jesus instruct you the accuracy of fasting and its methods?
How do you know what precautions to take whilst fasting? What if you accidentally eat or drank does this nullify your fast?
Where are the instructions rules and regulations for fasting found in the gospels ?
How did Jesus fast and what did he recommend for you Christians since you call yourself his devout followers?
When did Jesus break his fast and what did he break his fast with?
How do you know your fasting is accepted as it follows the criteria of the fasting which Jesus himself did?
Can you show us from the gospels any of the above criteria of fasting or is it that your made it up yourself?
How did the early Christians fast do you have any documented records?
What types of food did Jesus and his followers eat after fasting?
What is the time like of fasting ?
Can a women fast when she's on her menses ?
What is permissible and impermissible whilst fasting?
Please enlighten us of your fasting procedures if you know yourself
What's amazing is, that Jesus did not inform you in how to fast or what type of actions are to be sanctioned during fasting. But he did say something which Christians are very familiar with, and that is
I have yet many things to say unto you, but ye cannot bear them now. Howbeit when the, the Spirit of truth, is come, he shall guide you into all the truth.... (John 16:12-13)
Notice the words used, Jesus has many things to tell them, but they cannot bear them now. However when the SPIRIT OF TRUTH ARRIVES HE WILL GUIDE THEM TO ALL TRUTH. This tell us Jesus did not bring All TRUTH
Rather it was Prophet Muhammed Pbuh who came with All Truth he taught us how to fast and what requirement are needed to fast. How fasting should be performed, in what way and for how long etc...