The Prophet ﷺ said, "Whoever prays six rakahs after Maghrib without speaking any evil between them, they will be reckoned for him as the equivalent of twelve years of worship."
حدثنا علي بن محمد حدثنا أبو الحسين العكلي أخبرني عمر بن أبي خثعم اليمامي أنبأنا يحيى بن أبي كثير عن أبي سلمة بن عبد الرحمن بن عوف
أن النبي ﷺ قال من صلى بعد المغرب ست ركعات لم يتكلم بينهن بسوء عدلن له بعبادة ثنتي عشرة سنة
Sourcing, [its chain of transmission is extremely daif], Tirmidhi transmitted it in the Book of Prayer, chapter on the merit of six voluntary units of prayer after Maghrib, hadith no. 435, from the hadith of Zayd bin Hubab Ukayli, with this chain, and he said, I heard Muhammad bin Ismail (Bukhari) say, Umar bin Abdullah bin Abu Khatham is munkar al-hadith, and he declared him extremely daif.