Col 3:23 And whatever you do, work heartily, as for the Lord, and not for men, ‘Do your work heartily’ sounds better than ‘do your work out of your soul’. However, here is the word psyche (ψυχή psychē), G5590 meaning: 1. the breath of life (animals or men) 2. life 3. that in which there is life (a living being) and also the soul.
The Apostle’s request comes out of the idea that our Christian deeds must come from genuine love of the neighbor, that is, from ‘heart’. ‘Heart’ is believed to be the dwelling place of human feelings, the will to do good or evil. A man is said to be warm-hearted or he is cold at heart. During the 1970s, Jehovah’s Witnesses wrote articles where they tried to prove that the heart really is the place in the human body where such thoughts arise. Nowadays everyone agrees that thoughts come from the brain, and the heart is just a descriptive place for thoughts.
A few examples about heart:
Rom 5:5 and hope doesn’t disappoint us, because God’s love has been poured out into our hearts through the Holy Spirit who was given to us. 2 Cor 1:22 who also sealed us, and gave us the down payment of the Spirit in our hearts.
Mat 13:15 ’For this people’s heart has grown callous, their ears are dull of hearing, they have closed their eyes; Or else perhaps they might perceive with their eyes, hear with their ears, understand with their heart, and should turn again; and I would heal them.’
Act 4:32 The multitude of those who believed were of one heart and soul. Not one of them claimed that anything of the things which he possessed was his own, but they had all things in common.
Rom 8:27 He who searches the hearts knows what is on the Spirit’s mind, because he makes intercession for the saints according to God.
1 Cor 4:5 Therefore judge nothing before the time, until the Lord comes, who will both bring to light the hidden things of darkness and reveal the counsels of the hearts. Then each man will get his praise from God.
Heb 3:12 See to it, my brothers, that no evil, unbelieving heart is found in any of you, as shown by your turning away from the living God.
2 Pet 2:14 having eyes full of adultery, and who can’t cease from sin; enticing unsettled souls; having a heart trained in greed; children of cursing;