The Israelites tithed 30% of their income

Tithe -

a tenth of the produce of the earth consecrated and set apart for special purposes. The dedication of a tenth to God was recognized as a duty before the time of Moses. Abraham paid tithes to Melchizedek (Gen. 14:20; Heb. 7:6); and Jacob vowed unto the Lord and said, "Of all that thou shalt give me I will surely give the tenth unto thee."

The first Mosaic law on this subject is recorded in Lev. 27:30-32. Subsequent legislation regulated the destination of the tithes (Num. 18:21-24, 26-28; Deut. 12:5, 6, 11, 17; 14:22, 23). The paying of the tithes was an important part of the Jewish religious worship. In the days of Hezekiah one of the first results of the reformation of religion was the eagerness with which the people brought in their tithes (2 Chr. 31:5, 6). The neglect of this duty was sternly rebuked by the prophets (Amos 4:4; Mal. 3:8-10). It cannot be affirmed that the Old Testament law of tithes is binding on the Christian Church, nevertheless the principle of this law remains, and is incorporated in the gospel (1 Cor. 9:13, 14); and if, as is the case, the motive that ought to prompt to liberality in the cause of religion and of the service of God be greater now than in Old Testament times, then Christians outght to go beyond the ancient Hebrew in consecrating both themselves and their substance to God.

Every Jew was required by the Levitical law to pay three tithes of his property (1) one tithe for the Levites; (2) one for the use of the temple and the great feasts; and (3) one for the poor of the land.

...There is thus an obvious apparent discrepancy between the legislation in Leviticus and Deuteronomy. It is harmonized in Jewish tradition, not only theoretically but in practice, by considering the tithes as three different tithes, which are named the First Tithe, the Second Tithe, and the Poor Tithe, which is called also the Third Tithe (Pe'ah, Ma`aseroth, Ma`ser Sheni, Dema'i, Ro'sh ha-shanah; compare Tobit 1:7,8; Ant, IV, iv, 3; viii, 8; viii, 22). According to this explanation, after the tithe (the First Tithe) was given to the Levites (of which they had to give the tithe to the priests), a Second Tithe of the remaining nine-tenths had to be set apart and consumed in Jerusalem. Those who lived far from Jerusalem could change this Second Tithe into money with the addition of a 5th part of its value. Only food, drink or ointment could be bought for the money (Ma`aser Sheni 2 1; compare Dt 14:26). The tithe of cattle belonged to the Second Tithe, and was to be used for the feast in Jerusalem (Zebhachim 5 8). In the 3rd year the Second Tithe was to be given entirely to the Levites and the poor. But according to Josephus (Ant., IV, viii, 22) the "Poor Tithe" was actually a third one. The priests and the Levites, if landowners, were also obliged to give the Poor Tithe (Pe'ah 1 6).[NET Bible Study Dictionary]