信守不渝 meaning in English

be unswervingly true; be unswervingly faithful

Our benefactor knows his lofty destiny , and will be true to it
我们的恩人知道自己的崇高天职，他必将信守不渝。
Monsieur mon frre , i learnt yesterday that in spite of the loyalty with which i have kept my engagements with your majesty , your troops have crossed the frontiers of russia , and i have this moment received from petersburg the note in which count lauriston informs me as cause of this invasion that your majesty considers us to be in hostile relations ever since prince kurakin asked for his passport
虽然对陛下所负的义务，我信守不渝，但昨天我得悉您的军队越过了俄国边境，直到现时我才收到从彼得堡送来的通牒，洛里斯东伯爵在谈到这次进犯，引用通牒的话对我说，自从库拉金公爵申请自己的护照时起，陛下就认为您和我彼此都怀有恶感。