天地为证日月为鉴
[tiān dì wéi zhèng rì yuè wéi jiàn]
'Heaven and Earth as Witnesses; Sun and Moon as Mirrors' indicates using the cosmos and celestial bodies as witnesses and proof to one's promise or vow. It carries a sense of grandiose commitment and eternal reliability beyond human scale, demonstrating determination, dedication, and unwavering commitment that transcends life itself.