The Prophet (ﷺ) said: The supplication which gets the quickest answer is that made by one distant Muslim for another.
Sunan Abi Dawud Book 8, Hadith 120
← Previous Hadith I heard the Messenger of Allah (ﷺ) say: When a Muslim supplicates for his absent brother the angels say: Amin, and may you receive the like.

Sunan Abi Dawud Book 8, Hadith 119 Next Hadith → The Prophet (ﷺ) said: Three supplications are answered, there being no doubt about them; that of a father, that of a traveller and that of one who has been wronged.

Sunan Abi Dawud Book 8, Hadith 121