What qualifies you as an intercessor?

David’s opening words add ballast to his prior confession, not only clearing the people but also seeking to reconcile his own relationship with YHWH, thereby making himself a more credible intercessor. [footnote: Compare the instructions to Aaron to make confession on behalf of himself and his household (Lev 16:6, 11) prior to confessing his people’s sins (Lev 16:16). In the eyes of the biblical writers, David may not have been considered eligible to intercede if burdened with unconfessed sin.]—Forestalling Doom page 197

<idle musing>
In other words, "Therefore, if you bring your gift to the altar and there remember that your brother or sister has something against you, leave your gift at the altar and go. First make things right with your brother or sister and then come back and offer your gift." (Matt 5:23 CEB).

So, to answer the question:

Who can ascend the Lord’s mountain?
Who can stand in his holy sanctuary?
Only the one with clean hands and a pure heart;
the one who hasn’t made false promises,
the one who hasn’t sworn dishonestly.
That kind of person receives blessings from the Lord
and righteousness from the God who saves.

Holiness matters...and I'm talking heart holiness, not rule-based pseudo-holiness. You know, the kind that is imparted by the Holy Spirit.
</idle musing>