Those who are on the frontier and their deeds

Question

What does the Hadith below mean? :

Narrated Fadalah ibn Ubayd:

The Prophet (ﷺ) said: Everyone who dies will have fully complete his action, except one who is on the frontier (in Allah's path), for his deeds will be made to go on increasing till the Day of Resurrection, and he will be safe from the trial in the grave. (Sunan Abi Dawud 2500)

Who are those that are on the frontier? What does it mean that their deeds will continuously increase?

Does it refer to the Prophets and the martyrs? Righteous deeds like praying and doing dhikr are still being performed by them even after they have died. Likewise, the deeds of the Prophets are continuously increasing because of the teachings and commandments that they brought as per the Hadith here. Is this interpretation correct?

Answer 1

رباط - It refers to those guarding the frontiers (borders) between the Muslims and the Kuffar, being ever prepared to fight. The same are mentioned in the verse 3:200, and muhaditheen have established chapters on it in their collections such as in Bukhari, Muslim, Ibn Majah, Nasai, Tirmidhi etc.

They are distinct from martyrs in that the martyrs are those who are killed in fighting, while in this case the virtue is proven even if they die naturally while performing their service.

Answer 2

Means everyone after death will gain no more rewards/sins closed his book. Except the one who fight in path of Allah he will continue gaining rewards growing rewards until the last day!