If our motive for giving is solely in order to receive, then our heart is not right with God. Life and everything we have is freely given to us by God. God demonstrates his love towards us in giving us the opportunity to attain to eternal life through Jesus Christ. In return we are asked to love God and our fellow man.
Mark 12:30 And thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind, and with all thy strength: this is the first commandment. 31 And the second is like, namely this, Thou shalt love thy neighbour as thyself.
Genuine love gives freely without expecting anything in return. The principle was enshrined in the Law given through Moses
Deuteronomy 15:7 If there be among you a poor man of one of thy brethren within any of thy gates in thy land which the LORD thy God giveth thee, thou shalt not harden thine heart, nor shut thine hand from thy poor brother: 8 But thou shalt open thine hand wide unto him, and shalt surely lend him sufficient for his need, in that which he wanteth. 9 Beware that there be not a thought in thy wicked heart, saying, The seventh year, the year of release, is at hand; and thine eye be evil against thy poor brother, and thou givest him nought; and he cry unto the LORD against thee, and it be sin unto thee. 10 Thou shalt surely give him, and thine heart shall not be grieved when thou givest unto him: because that for this thing the LORD thy God shall bless thee in all thy works, and in all that thou puttest thine hand unto. 11 For the poor shall never cease out of the land: therefore I command thee, saying, Thou shalt open thine hand wide unto thy brother, to thy poor, and to thy needy, in thy land.
The promise is that those who give freely will be blessed by God (v10). To be blessed by God is not necessarily a blessing in material things in this life. Blessing in this life is transient, for we all die. The blessing we seek is eternal life at the resurrection of the dead.
The same advice concerning giving appears in Proverbs:
Proverbs 11:25 The liberal soul shall be made fat: and he that watereth shall be watered also himself.
Proverbs 19:17 He that hath pity upon the poor lendeth unto the LORD; and that which he hath given will he pay him again.
Proverbs 22:9 He that hath a bountiful eye shall be blessed; for he giveth of his bread to the poor.
And in Ecclesiastes
Ecclesiastes 11:1 Cast thy bread upon the waters: for thou shalt find it after many days. 2 Give a portion to seven, and also to eight; for thou knowest not what evil shall be upon the earth.
Christ gives the following instruction
Matthew 5:42 Give to him that asketh thee, and from him that would borrow of thee turn not thou away.
Luke 6:34 And if ye lend to them of whom ye hope to receive, what thank have ye? for sinners also lend to sinners, to receive as much again. 35 But love ye your enemies, and do good, and lend, hoping for nothing again; and your reward shall be great, and ye shall be the children of the Highest: for he is kind unto the unthankful and to the evil. 36 Be ye therefore merciful, as your Father also is merciful... 38 (NKJV) "Give, and it will be given to you: good measure, pressed down, shaken together, and running over will be put into your bosom. For with the same measure that you use, it will be measured back to you."
Luke 14:12 Then said he also to him that bade him, When thou makest a dinner or a supper, call not thy friends, nor thy brethren, neither thy kinsmen, nor thy rich neighbours; lest they also bid thee again, and a recompence be made thee. 13 But when thou makest a feast, call the poor, the maimed, the lame, the blind: 14 And thou shalt be blessed; for they cannot recompense thee: for thou shalt be recompensed at the resurrection of the just.
Here we see that we will be rewarded for our giving at the resurrection of the just.
Acts 20:35 I have shewed you all things, how that so labouring ye ought to support the weak, and to remember the words of the Lord Jesus, how he said, It is more blessed to give than to receive.
2 Corinthians 8:12 For if there be first a willing mind, it is accepted according to that a man hath, and not according to that he hath not.
2 Corinthians 9:7 Every man according as he purposeth in his heart, so let him give; not grudgingly, or of necessity: for God loveth a cheerful giver.
Philippians 4:11 Not that I speak in respect of want: for I have learned, in whatsoever state I am, therewith to be content.
Thus our motivation for giving according to the will of God should not be for a reward in this life but rather that we might attain to eternal life in the world to come when Christ returns.
I hope you have found this helpful.