John Trapp on Psalms 66:18

Verſ. 18. If I regard iniquity in mine heart] If I have but a [illegible: 1 letter]exths-mind to it, as we ſay; If I caſt but a leering-look towards it, if there be in mee but an irreſolution againſt it; how much more then if I allow it and wallow in i[illegible: 2 letters] He who chuſeth to hold faſt ſin, doth, by his own election, forſake mercy, Jon. 2.8. neither let ſuch a man think that he ſhall receive any thing at the hands of God, Jam. 1.7. As in a wound, a plaſter prevaileth not, whiles the Iron remaineth within; ſo neither prayer, while ſin rankleth. God will never accept of a good motion from a bad mouth, as that State in ſtory would not. A man may deliver an excellent ſpeech, but becauſe of his ſtinking breath, we may have no pleaſure to hear him: ſo in this caſe. Prayer is a pouring out of the heart, as hath been already obſerved. If iniquity harbour there, prayer is obſtructed, and if it do break out, it will have the ſcent and ſavour of that iniquity upon it, and thereby diſpleaſe. Kimchi maketh this ſtrange ſenſe (quite from the purpoſe, and from the truth) If I regard iniquity only in my heart, ſo that I break not forth into outward act; God will not hear, i. e. ſo hear, as to impute it, or to account it a ſin. Phariſaice.