This is an idiom. This does not mean God forgot something. The writer is asking God to think about and consider his acts of compassion and faithfulness. AT: "Remember" or "Think about" (See: [[rc://en/ta/man/translate/figs-idiom]])
The abstract nouns "compassion" and "faithfulness" can be stated as adjectives. AT: "how you have been compassionate and faithful to your covenant" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
Here "they" personifies God's compassion and covenant faithfulness. AT: "for that is how you have always been" (See: [[rc://en/ta/man/translate/figs-personification]])