Shemos 25:2 states:
וְיִקְחוּ־לִ֖י תְּרוּמָ֑ה מֵאֵ֤ת כׇּל־אִישׁ֙ אֲשֶׁ֣ר יִדְּבֶ֣נּוּ לִבּ֔וֹ תִּקְח֖וּ אֶת־תְּרוּמָתִֽי׃
And they should take for me a donation from any man who wishes to donate his heart, they should take his donation.
This is carried out in Shemos 35:22:
כל נדיב לב הביאו
Each man who donated his heart brought it
How could the Torah be Matir a heart transplant if Rav Moshe says it is Assur? (See this article.)