Psalms 89:49

Lord, where are thy former loving-kindnesses - Thy mercies; thy pledges; thy promises. Where are those promises which thou didst make formerly to David? Are they accomplished? Or are they forgotten and disregarded? They seem to be treated as a thing of nought; as if they had not been made. He relied on them; but they are not now fulfilled.

Which thou swarest unto David - Which thou didst solemnly promise, even with the implied solemnity of an oath.

In thy truth - Pledging thy veracity.