Ephesians 4:29 Let no corrupt communication proceed out of your mouth, but what is good for necessary edification, that it may impart grace to the hearers.
Speaking in grace has two meanings. The first is speaking in divine favor, which comes as a result of spending time in prayer before speaking. This enables you to say things from the Lord to help the person you are speaking to.
Many time others are looking for answers, and don’t know which way to turn. The Lord knows what they need, and shows you what to say. The second meaning is speaking in kindness and this helps build others.
Many times people have said things they later regretted, because they were not speaking in grace or love. Lack of tact can be over-come through prayer, because divine favor will help your thoughts before the words are spoken.