Matthew Poole's English Annotations on the Holy Bible - Psalms 18:26
Pure; free from the least mixture or appearance of unrighteousness, or unfaithfulness, or unkindness; or simply and sincerely, such as thou usest and hast promised to be to them that are such; for purity is oft put for sincerity. Froward, or perverse, i.e. thou wilt cross him, and walk contrary to him, as thou hast threatened, Leviticus 26:23,Leviticus 26:24. See also Proverbs 3:34. Man’s perverseness here is moral and sinful, but God’s perverseness is judicial and penal. read more
Matthew Poole's English Annotations on the Holy Bible - Psalms 18:25
Upright, or sincere, to wit, in performing what thou hast promised to such persons, this being a great part or act of sincerity, when one’s deeds and words, or professions, agree together; as, on the contrary, for those that deal hypocritically and wickedly with thee, thou wilt make them to know thy breach of promise, as it is expressed, Numbers 14:34. The sense of the verse is, Thou metest to every one the same measure which he meteth out to others, and givest to him the fruit of his own... read more