Most likely, people went around with long faces/a demeanour that encouraged others to ask what was wrong so that they could tell them that they were fasting.1 It may be that people also wore different clothes and put ashes on their head (see Daniel 9:3; Jonah 3:5),2 or afflicted themselves in some other way (Leviticus 23:32).3 By making sure that everyone knew you were fasting, it was no longer a righteous activity done for the purpose of drawing near to God,4 but an act to win the approval and praise of your fellow man.5
16 Lorsque vous jeûnez, ne prenez pas un air triste, comme les hypocrites, qui se rendent le visage tout défait, pour montrer aux hommes qu'ils jeûnent. Je vous le dis en vérité, ils ont leur récompense.