26 The Lord spoke to Moses, saying, 27 “On exactly the tenth day of this seventh month is the day of atonement; it shall be a holy convocation for you, and you shall humble your souls and present an offering by fire to the Lord. 28 You shall not do any work on this same day, for it is a day of atonement, to make atonement on your behalf before the Lord your God. 29 If there is any [e]person who will not humble himself on this same day, he shall be cut off from his people. 30 As for any person who does any work on this same day, that person I will destroy from among his people. 31 You shall do no work at all. It is to be a perpetual statute throughout your generations in all your dwelling places. 32 It is to be a sabbath of complete rest to you, and you shall humble your souls; on the ninth of the month at evening, from evening until evening you shall keep your sabbath.”
33 Again the Lord spoke to Moses, saying, 34 “Speak to the sons of Israel, saying, ‘On the fifteenth of this seventh month is the Feast of Booths for seven days to the Lord. 35 On the first day is a holy convocation; you shall do no laborious work of any kind. 36 For seven days you shall present an offering by fire to the Lord. On the eighth day you shall have a holy convocation and present an offering by fire to the Lord; it is an assembly. You shall do no laborious work.
37 ‘These are the appointed times of the Lord which you shall proclaim as holy convocations, to present offerings by fire to the Lord—burnt offerings and grain offerings, sacrifices and drink offerings, each day’s matter on its own day—38 besides those of the sabbaths of the Lord, and besides your gifts and besides all your [f]votive and freewill offerings, which you give to the Lord.
39 ‘On exactly the fifteenth day of the seventh month, when you have gathered in the crops of the land, you shall celebrate the feast of the Lord for seven days, with a [g]rest on the first day and a [h]rest on the eighth day. 40 Now on the first day you shall take for yourselves the [i]foliage of beautiful trees, palm branches and boughs of leafy trees and willows of the brook, and you shall rejoice before the Lord your God for seven days. 41 You shall thus celebrate it as a feast to the Lord for seven days in the year. It shall be a perpetual statute throughout your generations; you shall celebrate it in the seventh month. 42 You shall [j]live in booths for seven days; all the native-born in Israel shall [k]live in booths, 43 so that your generations may know that I had the sons of Israel live in booths when I brought them out from the land of Egypt. I am the Lord your God.’” 44 So Moses declared to the sons of Israel the appointed times of the Lord.
Both of these next “convocations” appear to have come after the harvest (the Hebrew calendar is quite different than the modern one). Thus it was a time of celebration, when they would have plenty of crops and animals to celebrate over, and to offer to the Lord.
So instead of requiring them to offer sacrifices at times when food might have been getting a bit scarce, God has the kindness and compassion to wait until there was plenty. For God loves a cheerful giver, and He wasn’t going to “stack the deck” against them on that.
Likewise, it is for good reason we should give our offerings as the first thing we do after getting paid. Rather than waiting until you’ve just about run out and then neglecting one of God’s commands, especially if one lives “paycheck to paycheck”; if you give when you just got paid, it’s easier to be cheerful.