No man can serve two masters: for either he will hate the one, and love the other; or else he will hold to the one, and despise the other. Ye cannot serve God and mammon, Matthew 6:24.

Jesus did not say we must not, nor does He say we should not, but He does tell us we cannot serve God and mammon; we cannot love both. Where our heart is, there is our treasure. When building for gain becomes your treasure, you are no longer serving the Lord. It is impossible to serve God if your heart is set on something else.

1JO 2:15-17 says, "Love not the world, neither the things that are in the world. If any man love the world, the love of the Father is not in him. For all that is in the world, the lust of the flesh, and the lust of the eyes, and the pride of life, is not of the Father, but is of the world. And the world passeth away, and the lust thereof: but he that doeth the will of God abideth for ever." If you love the world and worldly things, the love of the Father is not in you.

The love of the world is a revelation of our enmity against God! JAM 4:4 says, "Ye adulterers and adulteresses, know ye not that the friendship of the world is enmity with God? whosoever therefore will be a friend of the world is the enemy of God." God says in PRO 23:26, "My son, give me thine heart, and let thine eyes observe my ways," but mammon says, "No! Give it to me!"

God says in PHI 4:5-6, "Let your moderation be known unto all men. The Lord is at hand. Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God. And the peace of God, which passeth all understanding, shall keep your hearts and minds through Christ Jesus."

Martha had complained to Jesus that her sister had left her to serve alone, "But Martha was cumbered about much serving, and came to him, and said, Lord, dost thou not care that my sister hath left me to serve alone? bid her therefore that she help me," LUK 10:40.

Martha was so concerned about serving that she missed the one thing needful. Sometimes we can have so many concerns that we focus our attention on them, and we are careful about them. Then we don't trust the Lord; then it is unbelief. We are troubled because our heart is not in the right posture.

See how Jesus reproved Martha for the mammon in her heart in LUK 10:41-42, "And Jesus answered and said unto her, Martha, Martha, thou art careful and troubled about many things: [PHI 4:5 says, `Be careful for nothing,' but Martha was careful and troubled about many things. Jesus says,] But one thing is needful: and Mary hath chosen that good part, which shall not be taken away from her."

What had Mary chosen? She was sitting at the feet of her Saviour, washing His feet with her tears, and wiping them with her hair; she was mourning over her sin. She wasn't so busy with serving in the temporal things, her heart was mourning over sin.