'Fast' in the Bible

But you who held fast to the Lord your God are alive today, every one of you.

For if you are careful to keep all this commandment which I am commanding you to do, to love the Lord your God, to walk in all His ways and hold fast to Him,

You shall go after Yahweh your God, and him you shall revere, and his commandment you shall keep, and to his voice you shall listen, and him you shall serve, and to him you shall hold fast.

by loving the Lord your God, by obeying His voice, and by holding fast to Him; for this is your life and the length of your days, that you may live in the land which the Lord swore to your fathers, to Abraham, Isaac, and Jacob, to give them.”