The fact of life is that money comes in one hand and soon after it leaves from the other. Money does not stay with us for long. So you have a choice of either wasting it on material possessions or spend it wisely in the service of Lord Krishna.
It is important to realize that everything, including your money, belongs to Lord Krishna. You are just a caretaker for a very short time. You can either spend it in the service of Lord Krishna by donating to His temples or devotees who are engaged in His service or spend it on yourself and waste it and incur sin on yourself.
“One who performs his duty without attachment, surrendering the results unto the supreme God, is not affected by sinful action, as the lotus leaf is untouched by water.” (Lord Krishna, Bhagavad-Gita 5.10)
Here Lord Krishna recommends that one should work for Him. This means that we should offer the results (pay checks) of our sacrifice (job) to Him (some of it at least). If we just enjoy the fruits (pay checks) of our sacrifice (job) results by ourselves, we are living in sin.
When should you donate?
Well, whenever you receive the fruits (pay check) of your sacrifices (job), you should offer the results (money) to Lord Krishna.
Are you going to take your Material Possessions with you?
At death you will leave behind everything you own, the money in the bank, the nice cars, the big houses, the gold jewelry and so on, and you will get another body according to your work. Every tiny bit of service to Lord Krishna will count towards determining your next body (human or animal) and its conditions of life (rich, poor, healthy, diseased etc.). If you have spent your life in serving Lord Krishna, then at the end you will go back to Him. If you have not served Him, then you will have to go through all the pains of life again, again, again, and again until in one of your future incarnations you finally realize that life is meant only for serving Lord Krishna and not for self-gratification. A materialist life is a wasted life. You then engage in the service of Lord Krishna and at death you are liberated from material existence.
“The steadily devoted soul attains unadulterated peace because he offers the result of all activities to me; whereas a person who is not in union with the divine, who is greedy for the fruits of his labor, becomes entangled.” (Lord Krishna, Bhagavad-Gita 5.12)
Donating money gives one the opportunity to become free from material attachments and thus material life. Those who do not donate simply waste the money on material possessions and become attached to a materialist life and become bonded to material life for many lifetimes.
It is not that you should give up everything in the service of Lord Krishna and live in a hut. One can live in a Taj Mahal and drive a Mercedes, and not live in sin. Provided the same was given to Lord Krishna too, via donations of equal value to His temples or devotees engaged in His service.
A foolish person works hard all his life, accumulating a big bank balance, properties, jewelry, fast cars, and other material possessions. Then he quits his body to take another, leaving behind everything. Because he spent the money on himself and did not offer the results of his work (money) to God, he lived in sin and his next body will be that of a beggar.
Leave your money to the Children?
Leave your children moral values with Vedic sanskar teachings and not material possessions. Money will only bewilder your children more and spoil them. They will be completely captivated by maya, the illusion that money is everything and thus your children will waste this rare human in a materialistic life and at death will again come back to suffer, life after life. Set your children free by giving them spiritual knowledge and Vedic sanskars (moral values). The topmost spiritual knowledge is contained in the Bhagavad-Gita and Srimad-Bhagavatam. This will enable them to become free from material life at the end of this life and send them back to the spiritual kingdom called Vaikuntha, where everyone lives in the same body eternally in complete bliss. It’s impossible to live eternally in the same body on planet Earth and even more impossible to live in complete bliss, even for a short time.
An intelligent person will spend some of his hard earned money on himself and give a portion of it in charity. Thus when he quits his body, he will be able to enjoy his wealth in his next body too, if he desires to stay in the material manifestation. He will be born in a rich family.
Do you ever wonder why some are born in rich families and some in poor families? Well now you know why.