This statement was true when Moses spoke to the children of Israel after giving giving them the commandments of God, it is true for us today, and will remain true to the end of time. Even though we are under a new covenant, God is keeping the promise to us that if we believe on His Son (Mark 16:16, John 11:25), repent of our sins (Mark 1:15, Luke 13:3), confess Him before men (Matthew 10:32, Luke 12:8) , are baptized into Christ's death (John 3:1-7, I Peter 3:21) and live faithful to Him until death (Revelation 2:10), He will give us a crown of life.
"Also with the lute I will praise You— And Your faithfulness, O my God! To You I will sing with the harp, O Holy One of Israel."
- Psalm 71:22
As proclaimed by David, we too should praise God and His faithfulness. For without Him by our side, leading us through this world of woe, we would be lost and afraid.
"O LORD God of hosts, Who is mighty like You, O LORD? Your faithfulness also surrounds You."
- Psalm 89:8
Those who are in a true relationship with God cannot help but "see" the faithfulness with which He is surrounded. Reading His word we see over and over again how God has kept His promises, even when man tried to take matter into His own hands. Consider the story of Abraham and Sarah when Sarah told Abraham to go into her maidservant to produce an heir, because she had yet to bear any children (Genesis 16:1-4). God had promised Abraham that his descendants would be as the stars (Genesis 15:5), but yet when God told Abraham that Sarah would conceive at the age of 90 he laughed (Genesis 17:15-18). Despite Abraham's laughter at God's promise and the fact that he had a child through Hagar, God kept His promise and Sarah conceived and bore a son, and they called his name Isaac, as God commanded (Genesis 17:19, Genesis 21:1-3). God was faithful to Abraham, He will be faithful to us, too.
"God is faithful, by whom you were called into the fellowship of His Son, Jesus Christ our Lord."
- 1 Corinthians 1:9
"No temptation has overtaken you except such as is common to man; but God is faithful, who will not allow you to be tempted beyond what you are able, but with the temptation will also make the way of escape, that you may be able to bear it."
- 1 Corinthians 10:13
God loves and His sincere desire is for us to be in Heaven with Him. Therefore, even though He allows Satan to tempt us, that we might be tested and grow stronger in our faith, He "will not allow us to be tempted beyond what [we] are able," and "will also make the way of escape." God wants us to overcome sin, and is always there to help us if only we will seek the way of escape, acknowledging Him as our strength. Without God, we would have no hope of overcoming sin, and therefore no hope of eternal life with Him in heaven.