Allah says in the Qur’an:
و قولوا للناس حسنا (البقرة ٨٣)
Speak good to the people.
The ulema say this entails saying things in a nice way, with gentleness, without harshness or sternness and nice words.
This is with Muslims and non Muslims, mother and wife, father and children, someone you know and someone you don’t know.
If we look at ourselves, we don’t do this enough at all! Allah forgive us our shortcomings for they are far too great!