
Regular verb: fast - fasted - fasted
Simple form | V-ing form | 
| I must fast you must fast he must fast we must fast you must fast they must fast  | I must be fasting you must be fasting he must be fasting we must be fasting you must be fasting they must be fasting  | 
Perfect | V-ing perfect | 
| I must have fasted you must have fasted he must have fasted we must have fasted you must have fasted they must have fasted  | I must have been fasting you must have been fasting he must have been fasting we must have been fasting you must have been fasting they must have been fasting  | 
Simple form | V-ing form | 
| I mustn't fast you mustn't fast he mustn't fast we mustn't fast you mustn't fast they mustn't fast  | I mustn't be fasting you mustn't be fasting he mustn't be fasting we mustn't be fasting you mustn't be fasting they mustn't be fasting  | 
Perfect | V-ing perfect | 
| I mustn't have fasted you mustn't have fasted he mustn't have fasted we mustn't have fasted you mustn't have fasted they mustn't have fasted  | I mustn't have been fasting you mustn't have been fasting he mustn't have been fasting we mustn't have been fasting you mustn't have been fasting they mustn't have been fasting  | 
Simple form | V-ing form | 
| must I fast? must you fast? must he fast? must we fast? must you fast? must they fast?  | must I be fasting? must you be fasting? must he be fasting? must we be fasting? must you be fasting? must they be fasting?  | 
Perfect | V-ing perfect | 
| must I have fasted? must you have fasted? must he have fasted? must we have fasted? must you have fasted? must they have fasted?  | must I have been fasting? must you have been fasting? must he have been fasting? must we have been fasting? must you have been fasting? must they have been fasting?  | 
Simple form | V-ing form | 
| mustn't I fast? mustn't you fast? mustn't he fast? mustn't we fast? mustn't you fast? mustn't they fast?  | mustn't I be fasting? mustn't you be fasting? mustn't he be fasting? mustn't we be fasting? mustn't you be fasting? mustn't they be fasting?  | 
Perfect | V-ing perfect | 
| mustn't I have fasted? mustn't you have fasted? mustn't he have fasted? mustn't we have fasted? mustn't you have fasted? mustn't they have fasted?  | mustn't I have been fasting? mustn't you have been fasting? mustn't he have been fasting? mustn't we have been fasting? mustn't you have been fasting? mustn't they have been fasting?  |