'Sincerity' in the Bible

"So now, revere Yahweh and serve him in sincerity and faithfulness; remove the gods that your ancestors served beyond the river and in Egypt, and serve Yahweh.

"So then, if you have acted in good faith and sincerity in making Abimelech king, and if you have dealt well with Jerub-Baal and his house, and have dealt with him {according to his accomplishments}--

if you have acted in good faith and sincerity with Jerub-Baal and his house this day, then rejoice in Abimelech, and let him also rejoice in you.