Rebbi says (Mishlei 10:7) "the remembrance of the Tzaddik is for blessing": When he mentions the Tzaddik, "the Life of the worlds" — (Psalms 145:17) "the L–rd is a tzaddik in all of His ways — let it be for blessing "Amen!"
When God's Name Is Mentioned, One Should Respond with Amen, Affirming
Mekhilta Tractate Pischa 16:28