What is the ruling on concealing testimony, with evidence from the Qur'an and Sunnah?

It is obligatory upon a Muslim to bear witness for the sake of Allah the Almighty, if they are certain of it, fear the loss of another's right by withholding it, and do not fear for themselves, their family, or their wealth. This is based on the words of Allah the Almighty: "And do not conceal testimony, for whoever conceals it - his heart is sinful. And Allah is knowing of what you do," and His saying: "And uphold testimony for Allah. That is instructed to whoever believes in Allah and the Last Day."