1 Timothy 4:5

‘For it is sanctified through the word of God and prayer.’

And the reason that all are good without distinction is that they have been ‘sanctified/made holy/separated to God’ through the word of God and prayer. ‘Through the word of God’ may be seen as indicating that the word of God has declared that these things come from God (Genesis 1:26-30; Psalms 104:14-15; Psalms 145:15-16), or that Jesus has declared all things ‘clean’ (Mark 7:19), although it could indicate a reading or reciting of the word of God over the meal. ‘Through prayer’ would indicate that because all that they received was accompanied by prayer as they dedicated both their food and themselves to Him it therefore made them ‘pure’. Compare Acts 10:15; Mark 7:19. This clearly refers to the prayer of thanksgiving. It is probably safe to say that in most cases our modern way of somewhat hastily ‘saying grace’ comes somewhat short of this.

The word 'sanctify, make holy', indicates ‘separation to God for His own purposes’. What is sanctified is then seen as God's, and because it is God's it must only be used for God's purposes. The object itself does not change, what changes is its status. As a consequence we can set things apart to God by prayer and thereby 'sanctify' them. And once we have done so they become God's and must be used only according to His will and instruction., for once we have 'sanctified' them God sees them as His and as sanctified.

As we have seen the point that Paul is making in 1 Timoithy 1 Timothy 4:5 probably has in mind 'unclean' foods (Leviticus 11:0). Such foods are the opposite of sanctified. They are 'unclean' (not acceptable to God as food for His hly people). They were not to be eaten by God's people because God's people were holy. But Paul is now saying that through the word of God (what God has spoken concerning the matter, especially through Jesus Christ - Mark 7:19) and through prayer (setting them apart to God) these unclean foods can be 'made holy', that is, able to be eaten by God's holy people withut contaminating them. No change takes place in the food. It is its status that changes. Sanctifying a food does not guarantee that it is edible or not poisonous. What it guarantees is that it will not ritually defile because it is set apart to God.