'Fast' in the Bible

but Christ is faithful as a Son over His [Father’s] house. And we are His house if we hold fast our confidence and sense of triumph in our hope [in Christ].

Inasmuch then as we [believers] have a great High Priest who has [already ascended and] passed through the heavens, Jesus the Son of God, let us hold fast our confession [of faith and cling tenaciously to our absolute trust in Him as Savior].

so that by two unchangeable things [His promise and His oath] in which it is impossible for God to lie, we who have fled [to Him] for refuge would have strong encouragement and indwelling strength to hold tightly to the hope set before us.

Let us seize and hold tightly the confession of our hope without wavering, for He who promised is reliable and trustworthy and faithful [to His word];