そう えば
sō ieba

Expression

1. now that you mention it; come to think of it; that reminds me; on that subject; speaking of which

Usually Written in Kana
そういえば、確 たしかに太郎 たろう かけました。
sō ieba tashikani tarōo mikakemashita.
Come to think of it, I did see Taro.