John Gill Commentary James 1:8

"a doubleminded man, unstable in all his ways." — James 1:8 (ASV)

A double minded man
A man of two souls, or of a double heart, that speaks and asks with an heart, and an heart, as in (Psalms 12:2) who halts between two opinions, and is at an uncertainty what to do or say, and is undetermined what to ask for; or who is not sincere and upright in his requests, who asks for one thing, and means another, and asks amiss, and with an ill design;

does not call upon God in truth, and in the sincerity of his soul; draws nigh to him with his mouth, and honours him with his lips, but his heart is far from him.

Such an one is unstable in all his ways ;
he is confused in his mind; restless in his thoughts, unsettled in his designs and intentions; inconstant in his petitions; uncertain in his notions and opinion of things; and very variable in his actions, and especially in matters of religion;

he is always changing, and never at a point, but at a continual uncertainty, both in a way of thinking and doing: he never continues long either in an opinion, or in a practice, but is ever shifting and moving.