The promise that God will never leave nor forsake His people occurs often in Scripture. It was given here through Moses to the children of Israel as they were preparing to enter the land promised long ago to Abraham. Two verses later, it was then repeated personally for Joshua, who was to be their leader in the coming battles.
Essentially the same promise had been made to Jacob as he began to assume his God-ordained role. "Behold, I am with thee," God had said, ". . . for I will not leave thee, until I have done that which I have spoken to thee of" (Genesis 28:15). It was again repeated directly to Joshua by God. "As I was with Moses, so I will be with thee: I will not fail thee, nor forsake thee" (Joshua 1:5).
David passed on the same promise to Solomon as he became responsible for the kingdom and for building the great temple. "|God| will not fail thee, nor forsake thee, until thou hast finished all the work for the service of the house of the LORD" (1 Chronicles 28:20). "I the God of Israel will not forsake them" (Isaiah 41:17) was the Lord's promise still later to the faithful Israelites.
And we can rejoice today in this same wonderful promise. "He hath said, I will never leave thee, nor forsake thee. So that we may boldly say, The Lord is my helper, and I will not fear what man shall do unto me" (Hebrews 13:5-6). This remarkable verse has five negatives in the Greek, so that it could even be rendered literally as something like: "I will never, never leave thee, and never, never, never forsake thee." Surely this is one of the greatest of God's "exceeding great and precious promises" (2 Peter 1:4). HMM
http://www.icr.org/article/7026/