Our Faith is based on God's faithfulness, His trustworthiness and total reliability.
The word "pistis" which is usually translated as faith, also encompasses the idea of faithfulness, reliability, trustworthiness.
In Hebrew, one of the words for faith is emunah, from which is derived the word "Amen" ("so be it" or "so it is").
The thought behind Amen is "Let it be confirmed." The root meaning is "firm", "reliable".
Both meanings: "trust" and "trustworthiness" come together in the nature of God HImself.
The reason why we have faith (trust) in God, is because of God's trustworthiness.
As we grow in faith, the Holy Spirit is able to impart to us God's trustworthiness.
There are three Hebrew words that are closely related and help elucidate the meaning of God's faithfulness.
The words are emunah, chesed and berith.
Emunah we have looked at above.
Chesed (often translated "lovingkindness") is the expression of God's free, unmerited grace. The Hebrew greeting "chesed u shalomI" is the greeting Paul uses so often in his letters: Grace and Peace.
Chesed goes beyond anything that man can ever deserve or demand as a right. It is always based on a covenant that God enters into of His own initiative and volition.
Berith is God's voluntary and self-initiated covenant with mankind or specifically with an individual or nation.
We can combine these meanings by saying that chesed is God's trustworthiness in fulfilling Hi covenant commitments which He entered into voluntarily, and which go beyond anything we can deserve or demand.
The close connection between emunah, chesed and berith God's trustworthiness, grace (lovingkindness), and covennt is seen as the theme of the following verses in Psalm 89 where mercy is the alternate translation for lovingkindness.