The causative: instructions and permission
A causative relates someone to an action they cause or allow another person to perform. Use the context to distinguish instructions from permission and identify who acts.
Building causative forms
For group 1, use the a-row form plus せる: 飲む → 飲ませる and 買う → 買わせる. A verb ending in う takes わ here, not あ. For group 2, replace る with させる: 食べる → 食べさせる.
する becomes させる, and 来る becomes 来させる（こさせる）. Conjugate the resulting causative before adding endings such as ます or てください: 食べさせる → 食べさせます or 食べさせてください.
Who performs the action?
In 親は子どもに野菜を食べさせました, the parent had the child eat vegetables; the child did the eating. With an object such as 野菜を, learn this basic pattern in which 子どもに marks the person made or allowed to act.
子どもを公園で遊ばせました。 means someone let or had the child play in the park. It can express permission if the child wanted to play. The choice of に or を also depends on the verb and sentence structure, not a single universal rule.
Asking to be allowed to act
今日は早く帰らせてください。 asks to be allowed to leave early today. Usually, the speaker is the person who will leave. This differs from 帰ってください, which asks the other person to leave.
A causative does not always mean coercion. Nor does adding させてください automatically make a request unobtrusive. Consider whether permission is the other person's to give and whether the request needs an explanation.
Check: Who wants to rest in 少し休ませてください?
Show the answer and why
Usually the speaker is asking to be allowed to rest for a while. Compare 休んでください, which asks the other person to rest. The causative of 休む is 休ませる.