Assalamu'alaykumIs it sunnah to reply as وَأَنْتُمْ فَجَزَاكُمُ اللَّهُ خَيْرًا in response to جزاك الله خيرا.Please elaborate the reply with salaf statements as well on it.جزاك الله خيرا

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

It is confirmed in the Sunnah that the Prophet supplicated to the one who said to him "may Allah reward you with goodness”, by saying, “And you, may Allah reward you with goodness.”

This was reported by Ibn Hibbaan in his Saheeh from the Hadeeth of Usyad ibn Khudhayr who said:

“People from two different households came to me from my tribe: people from the household of Banu Thafar, and people from the household of Banu Mu’aawiyyah, and they said:

“Speak to the Prophet to give us (some money)”; so I spoke to the Prophet and he said: “Yes, give each household a portion, and whenever Allah blesses us with more, then we will give them more.” I said, “May Allah reward you with goodness, O Prophet of Allah.” He said: “And you, may Allah reward you with goodness; because what since I have known you, you have abstained (from asking people) and have been patient (through hardships).”

For more benefit, please refer to Fatwa 289741.

Allah knows best.