On the authority of Abu Sa’id (may Allah be pleased with him), who said that the Messenger of Allah (peace be upon him) said: Let not any one of you belittle himself.
They said: O Messenger of Allah, how can any one of us belittle himself?
He said: He finds a matter concerning Allah about which he should say something, and he does not say [it], so Allah (mighty and sublime be He) says to him on the Day of Resurrection: What prevented you from saying something about such-and-such and such-and-such? He says: [It was] out of fear of people. Then He says: Rather it is I whom you should more properly fear.
it indicates that we must not fear people to give witness to belittle himself but fear Allah.