Psalms 103:18

To such as keep his covenant, and to those that remember his commandments to do them.

The mercy and loving-kindness of God are from everlasting to everlasting, and His righteousness extends to children's children and through generations, to those who fear Him and keep His covenant and remember His commandments in order to do them. The covenant mercy and righteousness belong to and rest upon those who keep His covenant and remember His commandments by doing them. This is a strong assurance of faithfulness, justice, and covenant mercy, standing under the rule of His throne in heaven over all. That rule calls angels, hosts, and all His works to bless Him.

Keeping the commandments is a lived response to God's love, joined with believing, and obedience belongs with receiving the Father's love and peace. Keeping His commandments brings great reward even in this life, leaving the conscience uncondemned and the heart at peace with God instead of at enmity with Him. The promise requires solemn consideration of the shortness and uncertainty of human life. It requires taking warning from God's recorded dealings with His people from age to age, repenting and being converted, setting affection on things above and not on things that perish with the using, and seeking the riches that endure forever and the righteousness that never passes away.

The verse is among the psalms repeated by a growing company passing through a very narrow gate. The scene associates it with entry through the gate, while those unwilling to give up their idols are left behind.