Sirach 29:3

3 Keep thy word, and deal faithfully with him, and thou shalt always find the thing that is necessary for thee.

Sirach 29:3 In-Context

1 He that is merciful will lend unto his neighbour; and he that strengtheneth his hand keepeth the commandments.
2 Lend to thy neighbour in time of his need, and pay thou thy neighbour again in due season.
3 Keep thy word, and deal faithfully with him, and thou shalt always find the thing that is necessary for thee.
4 Many, when a thing was lent them, reckoned it to be found, and put them to trouble that helped them.
5 Till he hath received, he will kiss a man's hand; and for his neighbour's money he will speak submissly: but when he should repay, he will prolong the time, and return words of grief, and complain of the time.

The Brenton translation of the Septuagint is in the public domain.